Concatenating values in target column - vba

Question

I'm having troubles with a VBA code: There's an Excel sheet (Sheet1) that contains two essential columns (last & first name)
What I am trying to do is, that whenever you add another last and first name to the list, both of them automatically get concatenated in another sheet and form a new list (start position for that list is Sheet11.Range("AB3"), on position AB2 is the list title "Clients").
My code therefore was entered in Sheet1:
Private Sub Worksheet_Change(ByVal Target As Range)
Dim tmp As Range
For Each tmp In Sheet1.Range("C4:C100")
If tmp.Value <> "" And tmp.Offset(0, 1).Value <> "" Then
Sheet11.Cells(Cells(Rows.Count, "AB").End(xlUp).Row + 1, "AB").Value = tmp.Value & " " & tmp.Offset(0, 1).Value
End If
Next tmp
End Sub
Unfortunately, as soon as I enter first & last names while this code is active, the concatenated names are not listed one after another, but the last name in the list replaces the list title in AB2.
I guess the problem lies somewhere within the loop process, but I can't seem to figure out the logic behind it. I'd be thankful for any suggestions to solve that problem!

Answer 1

The problem is that the following instruction
Sheet11.Cells(Cells(Rows.Count, "AB").End(xlUp).Row + 1, "AB").Value
returns the same cell each time the loop is repeated. You can replace this whole line for example by this:
Range("AB" & tmp.Row).Value = tmp.Value & " " & tmp.Offset(0, 1).Value

Answer 2

Whenever you use a Worksheet_Change event macro to change the values of cell on the same worksheet, you need to turn off event handling or the value change will trigger a new event and the Worksheet_Change will try to run on top of itself. This also holds true for other worksheets that contain a Worksheet_Change unless you want the change in value to force the event. Similarly, the Target can represent more than a single cell (e.g. a paste operation) so you need to deal with the individual cells in the Intersect, not the Intersect as a whole.
Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Target, Columns("B:C")) Is Nothing Then
On Error GoTo bm_Safe_exit
Application.EnableEvents = False
Dim bc As Range
For Each bc In Intersect(Target, Columns("B:C"))
Sheet11.Cells(bc.Row, "AB") = _
Join(Array(Cells(bc.Row, "B").Value2, Cells(bc.Row, "C").Value2))
Next bc
End If
bm_Safe_exit:
Application.EnableEvents = True
End Sub
I've used the Join Function as the string concatenation mechanism. While any character can be supplied as a connector in a Join, the default is a space.

Answer 3

I suggest a faster Change event - you don't need to loop over all rows for every update
This will add new entries and update existing ones:
Private Sub Worksheet_Change(ByVal Target As Range)
With Target
If .CountLarge = 1 And .Row >= 3 And (.Column = 3 Or .Column = 4) Then
Dim cel As Range
Set cel = Cells(.Row, 3)
If Len(cel) > 0 And Len(cel.Offset(0, 1)) > 0 Then
Worksheets("Sheet11").Range("AB" & .Row) = cel & " " & cel.Offset(0, 1)
End If
End If
End With
End Sub