Worksheet Change Event

The Change Event is triggered when any cell in a worksheet is changed by the user or by any VBA application. Worksheet change event receives a Range object as its target argument.

VVBA code for validating data entry:

Private Sub Worksheet_Change(ByVal target As Range)
Dim myrng As Range, cell As Range
On Error Resume Next
Set myrng = Range("ValidRange")
   For Each cell In Intersect(myrng, target)
       If cell.Value > 12 Or cell.Value < 1 Then
            MsgBox "Please enter a value between 1 and 12"
            Range(cell.Address).Select
       End If
   Next cell
    Application.EnableEvents = True
End Sub