I found that a better alternative is to do the validation on the SQL side. It's very easy to use a sql RAISERROR function to display some meaningful feedback to the user, and you can stop the report execution!

Example:

IF (@intNumber > 55 OR @intNumber < 15)

RAISERROR('Error: Your number must be smaller than 55 and bigger than 15', 16, 0);

Syntax:

RAISERROR (@ErrorMessage, -- Message text.

@ErrorSeverity, -- Severity of >=16 stop the script and the Report execution.

@ErrorState -- State.

);