Question

Simply – if any cell in Column B contains thisvalue then append to the adjoining cell in Column A with sometext.

How is this done?

Answer 1

Put this formula in A1, then drag down as necessary:

=IF(B1="thisvalue","sometext","")

EDIT

Using a the Visual Basic Editor, you can update the contents of cell A like this:

Private Sub UpdateColumnA()
    Dim x As Long
    For x = 1 To 65536
        If InStr(1, Sheet1.Range("$B$" & x), "thisvalue") > 0 Then
            Sheet1.Range("$A$" & x) = Sheet1.Range("$A$" & x) & "sometext"
        End If
    Next
End Sub

Repeated runnings of the macro, however, will append the text again; you’ll need more validation code if you don’t want this to happen.