Displaying alert message based on user input on input param screen

Hi,

Based on user input I wish to display an alert popup on my report. I

have provided the user 2 dropdowns called sortasc and sortdesc with all

the column names used in the report to simulate dynamic sorting.This is

because we do not have dynamic sorting in CR XI R2. When the user

selects same column name in both sortasc and sortdesc then the sort

type which has priority in the record sort expert is executed. This is fine but we want an alert

or message popup displayed so as to prevent user from selecting same

column names.

I tried adding an alert with the following code:

if {?sortasc} = {?sortdesc} then true else false

So far I have not been prompted with any alert message box.

Let me know if there is any other option.