Copy the code below to a given worksheet codemodule. Once you do it
and save the excel workbook, on that particular sheet you would see
the cell graying out when you tab or move between range or cells.
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Dim mySht As Worksheet
Set mySht = Target.Parent
mySht.Cells.Interior.ColorIndex = 0
Target.Interior.ColorIndex = 15
End Sub