How to end infinite “change” loop in VBA

Question

I have a problem with visual basic. I want to make a macro/function that will multiply a number I enter by 3 and give a result in the same cell. I tried something like this:

Answer 1

You need to disable events to prevent recursion:

Sub Worksheet_Change(ByVal Target As Range)
    If Target.Address = "$Q$21" Then
        application.enableevents = false
        Target.Value = Target.Value * 3
        application.enableevents = true
    End If
End Sub

Just as an alternative, you can also use your own variable rather than tinkering with EnableEvents, though it will mean your code responds twice even though it doesn't actually do anything the second time round:

Dim bSkipEvents as Boolean
    Sub Worksheet_Change(ByVal Target As Range)
        If bSkipEvents then exit sub
        If Target.Address = "$Q$21" Then
            bSkipEvents = True
            Target.Value = Target.Value * 3
            bSkipEvents = False
        End If
    End Sub

This is also the sort of approach you need with userforms and most events for activex controls on worksheets.