Macro to add the IFERROR function to formulas

I spent time scouring the interwebs trying to find a macro that would add an "IFERROR" function to any formula for the cells that are selected. I found some code and modified it to be a little more custom, so apologies in that I don't know who to give credit to.

My issue with the below code is that if only have one cell selected, it loops through every cell in the worksheet and adds an IFERROR 'wrapper' to every formula. There seems like there should be a simple solution so that if you only have a single cell selected, the macro only applies to that cell.

Sub wrap()

    'Adds =IfError() around formulas
    Dim cel As Range
    Dim rng As Range
    Dim Check As String
    Dim userInput As String
    Dim Equ As String
    
    userInput = InputBox("What would you like the cell(s) to display if there's an error?")
   

    Equ = "=IFERROR(_x ,""" & userInput & """)"
        
    On Error Resume Next
    Set rng = Selection.SpecialCells(xlFormulas, 23)
    If rng Is Nothing Then Exit Sub
    
    With WorksheetFunction
        For Each cel In rng
            If Not cel.Formula Like Check Then
                cel.Formula = .Substitute(Equ, "_x", Mid$(cel.Formula, 2))
            End If
        Next
    End With
    
End Sub

I appreciate any feedback - thanks!!