Excel VBA: isna procedure & smart range selection

Hello experts,

I have the procedure reporting at the end of my message that I use from my personal.xlsb in order to compare values from different columns.
I would like to enhance the procedure by modifying the following:
1.      Instead of selecting the various range from top to down I would like to enter the column letter and the procedure should be able to display the range from initial top range till the last of used range and display input box “Range involved is equal to :”. This process should be applied for both columns
2.      Finish the procedure with the procedure by a filtering cells based on Interior.ColorIndex = "3"
3.      Display a Msgbox if the user cancels the procedure in of the range selection.
If you have questions, please contact me

Sub Is_Na()

Application.DisplayAlerts = False

Dim c As Range
On Error GoTo exit_routine_isna
Set UsedRange = Application.InputBox(prompt:="Please Select your range source, in this range you will find the cells wich are not in your range to compare", Title:="Range Select", Type:=8)
Set ComparisonRange = Application.InputBox(prompt:="Please Select Range to compare", Title:="Range Select", Type:=8)


For Each c In UsedRange
If IsNumeric(Application.Match(c, ComparisonRange, 0)) Then
Else: c.EntireRow.
End If
Next c Interior.ColorIndex = "3"
exit_routine_isna:
End Sub