How about:

Private Sub Worksheet_SelectionChange(ByVal Target As Excel.Range)
Dim l As Long
Dim strCells As String
     
Cells.Range("A3:M100").Interior.ColorIndex = xlColorIndexNone
     
l = ActiveCell.Row
If l < 3 Or l > 100 Then Exit Sub
strCells = "A" & l & ":F" & l
Cells.Range(strCells).Interior.Color = RGB(255, 200, 200)
End Sub