From the described scenario it sounds like you don't need to use a report parameter for X, since it will not be set by the user. Then it makes more sense to get this X value in some other way. Regardless if it is a constant, or set it via some logic in your application you can create your own user function (http://www.telerik.com/help/reporting/expressions-user-functions.html
), which will return the value for X and you can use the user function in expressions throughout the report. I hope this will work in your case.