Try this code:
Sub test()
Dim refToFind As String
Dim versToFind As String
refToFind = "ABC1"
versToFind = "1"
'address of first reference
Set Rng = Sheet1.Range("B2")
lastrow = Sheet1.Range("B" & Sheet1.Rows.Count).End(xlUp).Row - Rng.Row
For i = 0 To lastrow
If CStr(Rng.Offset(i, 0).Value) = refToFind _
And CStr(Rng.Offset(i, 1).Value) = versToFind Then
Rng.Offset(i, 4) = Now
End If
Next i
End Sub