Dynamic Parameters

I have a report that i want to beable to do some dynamic paramaters on it. I have a start and end date of when they want to run the report but i also have a mulivalue list box for users filtering for users. I want to add a supervisor filter on form also. But I have a problem.

I want to allow the users to select a supervisor and filter for all employees under that, or allow them to select a set of users and allow them to filter for that also. Also i would like when they select no supervisor or user it just filters for the dates and picks all up all the users.

I thought i could do something like in access like this Like UserName & "*"
but it doesnt work.

Here is my dataset code i am using currently:
SELECT U.Name, A.row_date, A.split, A.SumOfti_stafftime, A.AHT, A.AvgACW, A.AvgACD, A.AvailTime, A.SplitSkill_Incalls, A.SplitSkill_Outcalls, A.SumOfacdtime,
A.SumOfti_othertime, A.SumOfacwtime, A.SumOfti_auxtime0, A.SumOfti_auxtime1, A.SumOfti_auxtime2, A.SumOfti_auxtime3, A.SumOfti_auxtime4,
A.SumOfti_auxtime5, A.SumOfti_auxtime6, A.SumOfti_auxtime7, A.SumOfti_auxtime8, A.SumOfti_auxtime9, U.Sup
FROM tblAvayaDaily AS A RIGHT OUTER JOIN
tblUsers AS U ON A.logid = U.[Avaya ID]
WHERE (A.split = 1651) AND (U.Name IN (@UserName)) AND (A.row_date BETWEEN @rDateStart AND @rDateEnd) OR
(A.split = 1655) AND (U.Name IN (@UserName)) AND (A.row_date BETWEEN @rDateStart AND @rDateEnd) OR
(A.split = 1653) AND (U.Name IN (@UserName)) AND (A.row_date BETWEEN @rDateStart AND @rDateEnd)