I have using the following code for conditional formatting

Sub Worksheet_Change(ByVal Target As Range)
Dim Colour As Integer
    If Not Intersect(Target, Range("G3:M93")) Is Nothing Then
        Select Case Target
            Case "Sick"
               Colour = 6
            Case "Hol"
                Colour = 12
            Case "SUS"
                Colour = 7
            Case "N/A"
               Colour = 53
            Case "CPC"
               Colour = 15
            Case "ff"
                Colour = 42
            Case Else
        End Select
        Target.Interior.ColorIndex = Colour
    End If
End Sub
This works fine in itself however it only works if I put the code in a worksheet but I need it to apply to multiple worksheets (some are yet to be created). So when I put the code into "ThisWorkbook" the conditional formatting does not work.

Thank you