Re-reading the question I think you are probably correct Peter.

In which case using Application.InputBox the Type should be 2 for a string
and then use one of your methods to create the formula final formula.

Dim y As String

y = Application.InputBox(Prompt:="Enter Formula", Type:=2)

ActiveCell.Formula = "=IF(ISERROR(" & y & "),""""," & y & ")"

--
Regards,

OssieMac