need to automate report having user response in a date prompt variable

Hi,

I've a webi 4.0 report which is having date prompt as a input from the user. This report has multiple data providers and is using variable as

=FormatDate (ToDate(UserResponse("Report Date");"dd Mmm YYYY");"Mmmm YYYY") in the report. Report Date is the user prompt enabling user to input the date and is usually the last day of Month.

I want to automate the report so that user dont have to input the date in Report Date prompt. How do I implement this?

If I simply remove Report Date being used as a filter, report will run without asking user but this Report Date is being used as a variable and will #ERROR.

Please advise.

Thanks

Pritesh