Cancel a change in Worksheet Selection Change event
Private Sub Worksheet_SelectionChange(ByVal Target As Range) Dim Forbidden As Range
Set Forbidden = Union(Range("B10:F20"), Range("H10:L20")) If Intersect(Target, Forbidden) Is Nothing Then Exit Sub
Range("A1").Select
MsgBox "You can't select cells in " & Forbidden.Address, vbCritical End Sub