Can I capture and emulate a KeyDown event in Excel VBA?

Question

Arun Singh gave a great answer to a similar question (Is there any event that fires when keys are pressed when editing a cell?). I want to set a flag to prevent execution of Selection_Change event if the user is scrolling with the arrow keys.

Answer 1

It's pretty easy actually. I am demostrating it for UP and DOWN arrow key. You may add more to it like RIGHT/LEFT/TAB/ENTER etc... I have commented the part where you can add the keys.

Paste this in the worksheet code area

Option Explicit

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    If CancSelEvnt = False Then
        '
        '~~> Rest of the code for the Selection Change
        '
    Else
        '~~> Only for demostration purpose. Remove Msgbox later
        MsgBox "User pressed one of the navigation keys"

        CancSelEvnt = False
    End If
End Sub

Paste this in a module

Option Explicit

'~~> We need this as this will help us in cancelling the
'~~> Selection chnage event
Public CancSelEvnt As Boolean

Private Type POINTAPI
    x As Long
    y As Long
End Type

Private Type MSG
    hwnd As Long
    Message As Long
    wParam As Long
    lParam As Long
    time As Long
    pt As POINTAPI
End Type

Private Declare Function WaitMessage Lib "user32" () As Long

Private Declare Function PeekMessage Lib "user32" Alias "PeekMessageA" _
    (ByRef lpMsg As MSG, ByVal hwnd As Long, _
     ByVal wMsgFilterMin As Long, _
     ByVal wMsgFilterMax As Long, _
     ByVal wRemoveMsg As Long) As Long

Private Declare Function TranslateMessage Lib "user32" _
    (ByRef lpMsg As MSG) As Long

Private Declare Function PostMessage Lib "user32" Alias "PostMessageA" _
    (ByVal hwnd As Long, _
     ByVal wMsg As Long, _
     ByVal wParam As Long, _
     lParam As Any) As Long

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" _
    (ByVal lpClassName As String, _
     ByVal lpWindowName As String) As Long

Private Const WM_KEYDOWN As Long = &H100
Private Const PM_REMOVE  As Long = &H1
Private Const WM_CHAR    As Long = &H102
Private bExitLoop As Boolean

Sub StartKeyWatch()
    Dim msgMessage As MSG
    Dim bCancel As Boolean
    Dim iKeyCode As Integer
    Dim lXLhwnd As Long

    On Error GoTo errHandler:
    Application.EnableCancelKey = xlErrorHandler
    bExitLoop = False
    lXLhwnd = FindWindow("XLMAIN", Application.Caption)
    Do
        WaitMessage
        If PeekMessage _
            (msgMessage, lXLhwnd, WM_KEYDOWN, WM_KEYDOWN, PM_REMOVE) Then
            iKeyCode = msgMessage.wParam
            TranslateMessage msgMessage
            PeekMessage msgMessage, lXLhwnd, WM_CHAR, _
            WM_CHAR, PM_REMOVE
            If iKeyCode = vbKeyBack Then SendKeys "{BS}"
            If iKeyCode = vbKeyReturn Then SendKeys "{ENTER}"
            bCancel = False

            '
            '~~> This is the main part where we check what key is pressed
            '

            If iKeyCode = vbKeyDown Then   '<~~ Down
                SendKeys "{DOWN}"
                CancSelEvnt = True
            ElseIf iKeyCode = vbKeyUp Then '<~~ UP
                SendKeys "{UP}"
                CancSelEvnt = True
            '
            '~~> And so on for the rest of the navigation keys
            '
            Else
                CancSelEvnt = False
            End If

            If bCancel = False Then
                PostMessage _
                lXLhwnd, msgMessage.Message, msgMessage.wParam, 0
            End If
        End If
errHandler:
        DoEvents
    Loop Until bExitLoop
End Sub

Sub StopKeyWatch()
    bExitLoop = True
End Sub

And here is something that you may need ;)

VBKey Code List

vbKeyLButton    Left Mouse Button
vbKeyRButton    Right Mouse Button
vnKeyCancel     Cancel Key
vbKeyMButton    Middle Mouse button
vbKeyBack       Back Space Key
vbKeyTab        Tab Key
vbKeyClear      Clear Key
vbKeyReturn     Enter Key
vbKeyShift      Shift Key
vbKeyControl    Ctrl Key
vbKeyMenu       Menu Key
vbKeyPause      Pause Key
vbKeyCapital    Caps Lock Key
vbKeyEscape     Escape Key
vbKeySpace      Spacebar Key
vbKeyPageUp     Page Up Key
vbKeyPageDown   Page Down Key
vbKeyEnd        End Key
vbKeyHome       Home Key
vbKeyLeft       Left Arrow Key
vbKeyUp         Up Arrow Key
vbKeyRight      Right Arrow Key
vbKeyDown       Down Arrow Key
vbKeySelect     Select Key
vbKeyPrint      Print Screen Key
vbKeyExecute    Execute Key
vbKeySnapshot   Snapshot Key
vbKeyInsert     Insert Key
vbKeyDelete     Delete Key
vbKeyHelp       Help Key
vbKeyNumlock    Delete Key

vbKeyA through vbKeyZ are the key code constants for the alphabet
vbKey0 through vbKey9 are the key code constants for numbers
vbKeyF1 through vbKeyF16 are the key code constants for the function keys
vbKeyNumpad0 through vbKeyNumpad9 are the key code constants for the numeric key pad

Math signs are:
vbKeyMultiply      -  Multiplication Sign (*)
vbKeyAdd             - Addition Sign (+)
vbKeySubtract     - Minus Sign (-)
vbKeyDecimal    - Decimal Point (.)
vbKeyDivide        - Division sign (/)
vbKeySeparator  - Enter (keypad) sign

And Of course THIS msdn link for the key codes.

Answer 2

I need to adjust the above to work with Worksheet_Change and Tab key as basically when tab key is pressed then changes the Target (when A2 is edited and Tab key pressed, Change event shows cell B2) which I want to avoid.

I have changed the key part to:

        If iKeyCode = vbKeyTab Then   '<~~ Tab
            SendKeys "{TAB}"
            CancSelEvnt = True
        Else
            CancSelEvnt = False
        End If<code>

but am struggling to get any result on that?

When I press Tab key then my Change event does not call Sub StartKeyWatch() at all. also calling Sub StartKeyWatch() from Worksheet_Change directly does not seem to be doing anything...

what am I missing here?

thanks, mkvarious