Combo box in form (Access 2010) - Retrieving values from 2 different fields

Question

I need to create a Form on access 2010 that navigates among records from a table (t_main)

but the problem is that I need a combo to select among param1_old and new and also among param2_old and new.

This combo will have 2 values, the old and the new for each parameter. In the end, after I select which parameters I want to keep for this user, I will click in a button and save this information into a new table (t_saved).

t_main has the following structure:

user; date; name; param1_old; param1_new; param2_old; param2_new

and t_saved has the following structure:

user; date; name; param1; param2

Any idea on how to do that? Should I work with recordsets? is there a way to avoid it and just force the combo to take values from 2 different fields into a value list?

Thanks a lot for any help!

edit: I know it is rather complex to understand what I need, I will try to show in a screenshot:

the data in the table are as following:

user; date; name; param1_old; param1_new; param2_old; param2_new 1234568789;"21/07/2014";"John Smith";'Lemon street 125';'Avocado avenue 123'; '...'; '..'

Answer 1

You don't mention what is the primary key in each tables, so I will assume it's the user field and that each record in t_main and t_saved has a unique user.
If not, then substitute that with the actual primary key.

Note that date is a reserved keyword and you cannot name a field date, so I renamed it thedate instead.

I have created a small sample database that works as you describe (at least as I understand it).

I created these tables with some sample data:

I created a form bound to the t_main table:

Note that the dropdown boxes cbParam1 and cbParam2 are not bound to any field, they are left unbound.

The rowsource for the dropdown boxes is a bit of a hack, but it works well.
For instance, for cbParam1.RowSource:

SELECT param1_old 
FROM t_main 
WHERE user=Forms![FormMain]![User]

UNION ALL 

SELECT param1_new 
FROM t_main 
WHERE user=Forms![FormMain]![User];

This query selects both the old and new fields from the t_main record that has the same user as the one currently displayed. In effect, it shows both old and new parameters for the current record in the combobox.

The code behind the FormMain is mostly used to manage the display.
Here we prevent the user from adding the data to t_saved if one f the dropdown boxes is empty, or if we've already added that record before.

Option Compare Database
Option Explicit

' We use this variable to keep track of whether the
' record was already found in the t_saved table
Private alreadysaved As Boolean

'-----------------------------------------------------------------------------
' Update the UI after we change our selection of parameter
'-----------------------------------------------------------------------------
Private Sub cbParam1_AfterUpdate()
    UpdateUI
End Sub

Private Sub cbParam2_AfterUpdate()
    UpdateUI
End Sub

'-----------------------------------------------------------------------------
' Enable/Disable the save button.
' The button is only enabled if the user selected both parameters
'-----------------------------------------------------------------------------
Private Sub UpdateUI()
    btAddData.Enabled = Not (IsNull(cbParam1) Or IsNull(cbParam2)) _
                        And Not alreadysaved
End Sub

'-----------------------------------------------------------------------------
' Refresh teh data every time we change record
'-----------------------------------------------------------------------------
Private Sub Form_Current()
    ' Reset the values of the parameters comboboxes
    cbParam1 = Null
    cbParam2 = Null
    cbParam1.Requery
    cbParam2.Requery

    ' Check if there is already a record for the same user in the t_save table
    alreadysaved = DCount("user", "t_saved", "user='" & user & "'") > 0

    ' Display a warning to tell the user the current record cannot be saved again
    lblInfo.Visible = alreadysaved

    UpdateUI
End Sub

The important bit of code is actually the one that adds the data to a new record int he t_saved table:

'-----------------------------------------------------------------------------
' The button was clicked.
' Save the current record data to the t_save table
'-----------------------------------------------------------------------------
Private Sub btAddData_Click()
    ' We create a new new record in t_save and copy our data
    Dim db As DAO.Database
    Dim rs As DAO.Recordset
    Set db = CurrentDb()
    Set rs = db.OpenRecordset("t_saved", dbOpenDynaset, dbFailOnError)
    With rs
        .AddNew
            !user = user
            !thedate = thedate
            !name = name
            !param1 = cbParam1
            !param2 = cbParam2
        .Update
        .Close
    End With
    Set rs = Nothing
    Set db = Nothing

    ' Force the form to refresh itself
    ' This will cause the Form's OnCurrent event to be triggered
    Me.Requery
End Sub