Highlight doubleclicked cells of a specific range

Hello,

I have a program that allows for cells to be filled green then red and ten no fill for a given worksheet.(This occurs on doubleclick.) What I am trying to do is setup a way for the program to only be used for cells G2:Z1000.

Any help is appreciated,
Tay

HTML Code: 

One way perhaps:

Private Sub worksheet_beforedoubleclick(ByVal Target As Range, cancel As Boolean)
    Dim lngColor As Long
    If Not Intersect(Target, Range("G2:Z1000")) Is Nothing Then
        With Target
            Select Case .Interior.ColorIndex
                Case -4142
                    lngColor = 4
                Case 3
                    lngColor = -4142
                Case 4
                    lngColor = 3
            End Select
            .Interior.ColorIndex = lngColor
        End With
        Cancel = True
    End If
End Sub