How about using doubleclicking and rightclicking:
Option Explicit
Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, _
Cancel As Boolean)
If Target.Cells.Count > 1 Then Exit Sub
If Intersect(Target, Me.Range("A:A")) Is Nothing Then Exit Sub
Cancel = True 'stop editing in cell
Target.Value = "X"
End Sub
Private Sub Worksheet_BeforeRightClick(ByVal Target As Range, _
Cancel As Boolean)
If Target.Cells.Count > 1 Then Exit Sub
If Intersect(Target, Me.Range("A:A")) Is Nothing Then Exit Sub
Cancel = True 'stop pop up from showing
Target.Value = ""
End Sub
I used any cell in Column A. You can change that in both spots if you want.
Doubleclicking will add the X. Rightclicking will empty the cell.