Can I add something to this so that when the A1:A100 field is changed,
the whole row (A-L) is highlighted ColorIndex 6?

Dim x, cl

Private Sub Worksheet_Change(ByVal Target As Range)
If Intersect(Target, Range("A1:A100")) Is Nothing Then Exit Sub
Target.Offset(0, 1) = x
Target.Interior.ColorIndex = 6
End Sub

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
x = ActiveCell.Value
End Sub