Test 1
[VBA]
If IsDate("31/1/01") Then
'UK Date format
Else
'US Date format
End If
[/VBA]

Test 2
[VBA]Sub Yellow()
With Selection.Interior
If .ColorIndex = 6 Then
'Remove colour
.ColorIndex = xlNone
Else
'Set colour
.ColorIndex = 6
End If
End With
End Sub
[/VBA]