Option to Select Blank in Date Prompt

[abhi4u05]

I have a Date Prompt in which user will select the Resignation dates Range.I have made this date Prompt Optional so that if user it not selecting anything from this prompt by default this filter will not be applied in query. Now my Requirment is to give user option to select Blank also as there may be many Emplyee for which Resignation date will be Blank bcoz they are still with the Company. How go give this option in Date Prompt. I am using Cognos 8.4 Report Studio.

[CognosAdmn]

Not sure if/how it will work with Blank Dates.

But couldnt you give them another prompt for "Resigned" and "NotResigned"?
You could create another query calculation that has "Resigned" if a data is available and "NotResigned" if the date is blank. The prompt for those two options. If resigned is chosen, then prompt for the Resignation date range.

Or you could default the blank dates to a static value and then prompt for that value in a date prompt?

hope this helps.