How do I create the Stored Procedure and subsequent .rdl using Optional Date Parameters

So my Result set will have a TRANSACTION DATE, DATE EFFECTIVE, and DATE END. The Business User wants to utilize a Date Parameter using TRANSACTION DATEOR DATE EFFECTIVE AND DATE END range of dates.

My first question is how do I handle this within the Stored Procedure itself? Do I have to determine which dates are provided and then pro-grammatically massage my WHERE criteria based on IF...ELSE conditions??? Then within SSRS, how do I make my date parameters available or doesn't that matter since I'll handle it within my Stored Procedure? Are there any assumptions that have to be made here in terms of the rules for running this report? So the Business User knows they use one or the other and not both.

Thanks for your review and am hopeful for a reply.

PSULionRP