trigger vba or macro when leaving a cell...

This should be easy, and maybe I'm just missing something, but I want to run a macro or vba code when the user enters something into a specific cell and then moves to the next cell.

What is happening is that the user pastes a block of text into a cell, and it seems to really screw up the cell format. So when they move on to the next cell, I want to run a macro to reformat the cell I just left. In reality I have 4 specific cells they can enter data into, the rest are locked. The macro I have reformats all 4 cells, which is fine. I just can't figure out how to trigger it other than using a button...

THanks
Steve

something like this would work for you...
store this as code in your worksheet module

VB Code:

Private Sub Worksheet_SelectionChange(ByVal Target As Excel.Range)
 
    If ActiveCell = Range("A1") Then
        With Selection.Interior
        .ColorIndex = 10
        .Pattern = xlSolid
        End With
    ElseIf ActiveCell = Range("A2") Then
          With Selection.Interior
        .ColorIndex = 15
        .Pattern = xlSolid
        End With
    Else
        With Selection.Font
        .Name = "Arial"
        .Size = 14
        End With
    End If
End Sub