Skip Cells based on colour of cell

Hi there,

I have a macro where it will skip cells that have diagonal lines in the cell. This works well because i use it for data entry and sometimes theres a specific cell i don't need to put data into, therefore i put the diagonal lines in the cell and it will automatically skip the cell when entering the data. The VBA code is as follows:

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    If ActiveCell.Borders(xlDiagonalDown).LineStyle = xlContinuous Then
        ' Has Line, Select Next Cell
        ActiveCell.Offset(1, 0).Range("A1").Select
    End If
End Sub

Now i'm using conditional formatting to highlight these cells in a shade of grey but i can't conditionally format the cell to place the diagonal lines in. Is there a VBA code similar to above where i can have the cell skipped over based on the colour of the cell? The RGB colour of the grey i'm using is:
R: 128
G: 128
B: 128

Is this possible?

Thanks