How To Insert Numbers Or Rows For Missing Sequential Numbers In Excel?

I am looking at this kutools, and was trying to test a couple of the VBA scripts before I purchase the software. I have come across this one, and am wondering what needs to be changed to allow more than 2 columns.

This is the code you have on your site:

Sub InsertValueBetween()

'Update 20130825

Dim WorkRng As Range

Dim Rng As Range

Dim outArr As Variant

Dim dic As Variant

Set dic = CreateObject("Scripting.Dictionary")

'On Error Resume Next

xTitleId = "KutoolsforExcel"

Set WorkRng = Application.Selection

Set WorkRng = Application.InputBox("Range", xTitleId, WorkRng.Address, Type:=8)

num1 = WorkRng.Range("A1").Value

num2 = WorkRng.Range("A" & WorkRng.Rows.Count).Value

interval = num2 - num1

ReDim outArr(1 To interval + 1, 1 To 2)

For Each Rng In WorkRng

    dic(Rng.Value) = Rng.Offset(0, 1).Value

Next

For i = 0 To interval

    outArr(i + 1, 1) = i + num1

    If dic.Exists(i + num1) Then

        outArr(i + 1, 2) = dic(i + num1)

    Else

        outArr(i + 1, 2) = ""

    End If

Next

With WorkRng.Range("A1").Resize(UBound(outArr, 1), UBound(outArr, 2))

    .Value = outArr

    .Select

End With

End Sub

My issue is that sometimes I may have an excel spreadsheet that has columns A thru S, and other times I may have a sheet that has columns A thru Z. and my column that I need to base my add rows off of may not be the first one.

How can I modify this to allow me to select the entire spreadsheet, and then select the column that I want it to use for the sequential numbers?