Change Cell Color On Click And Reverse Macro

I am making a checklist for a Pda program. I need the active cell to highlight green and put an x in it for a specified range. This I have

The next part I cannot figure out -
after the cell have been highlighted once, and properly colored with an x, how can I get it to delete the fill and clear the x on the next click.

Dim x As Long
Private Sub Worksheet_SelectionChange(ByVal Target As Excel.Range)
' Set the highlighted cell to a color.
If Not Intersect(Target, Range("d28:d34")) Is Nothing Then
Target.Interior.ColorIndex = 4 ' green = true
'Set the highlighted cell to contain a text character
If Not Intersect(Target, Range("d28:d34")) Is Nothing Then
ActiveCell = "x"
End If
End If
End Sub