Calculating textboxes values grouped in diferent Lists

I have to Lists filtered by the same field. One List shows all records with the field IsClokedIn value = TRUE and the other list =FALSE. I have only one dataset that retrieve the ClockIn and Clock out for one user. In a perfect world, the user MUST clock in and always clock out. So, when i created my dataset i ordered by UserClockingID (whick is primary key). So, this MUST retrieve a dataset with alternate records IN / OUT (TRUE or FALSE)

Ex.

UserClokingID UserID Time IsClockedIN

2323 34 8:32:03 TRUE

2324 34 12:07:02 FALSE

2325 34 13:05:03 TRUE

2326 34 14:53:02 FALSE

2327 34 15:10:03 TRUE

2328 34 17:32:02 FALSE

All i need is to calculate (sum then divide by 60) the minutes returned by the method DateDiff between the first row in my TRUE filtered list and the first row in my FALSE filetered list... and so on for the 2nd, 3rd ..... I can get the minutes by taking the values directly from the Fields!IsClockedIn.Value and using a condition to "grab" the previous record if the current record ClockedIn.Value=FALSE. I already did that.

my problem is that when i try to perform a calculation of textboxes values(those with the ammount of minutes for every pair of records from the datalist) out of the group. It says you can only do that inside the group or dataregion.

Is there any work around?

I really need to get this solved.

Have you tried to sum the expression you are using to populate the textbox?|||

I couldn't. When you click on Preview automatically you get this error that you can't perform this out of the DataRegion that textbox belongs to. This is driving me crazy and I honestly think if this is not possible to do, then Reporting Services is missing something big here 'cause i'm sure i'm not the one trying to calculate fields in a List out of the list itself.