Another way without Marlett font but with Symbol font. Use the squareroot symbol. Place this in the sheet module.
CharlizePrivate Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean) If Target.Column = 1 And Target.Row > 1 Then ActiveCell.Font.Name = "Symbol" ActiveCell.Font.Size = 10 ActiveCell.FormulaR1C1 = "?" Cancel = True Else MsgBox ("Only column 1 and row > 1") Cancel = True End If End Sub