Initialize selection parameters not passed in SAP webgui URL

[h_frye]

I have a web dynpro abap application that provides a URL to a custom SAP transaction.  When a user clicks a PO number in the application, the URL launches the custom transaction and passes the PO number clicked and the DYNP_OKCODE to skip the first screen.  The URL is working fine for me, but for some users there is an issue with the selection parameters in the transaction code.  If I stop the URL at the selection screen, I can see that for me, no parameters are pre-filled except for the PO number passed in the URL.  For some users, though, there are additional selection fields pre-populated that skew the data results.  These are not fields passed as parameters in the URL, so I'm not sure how they are being populated.  I have confirmed that the transaction does not pre-populate values based on user parameter settings, nor are there any values coded as default values in the program code.  It almost seems as if the transaction retains values based on previous executions, but I cannot replicate that behavior.

Is there a way to initialize all selection parameters except for the ones passed in the URL?  The only work-around I know right now is to explicitly pass each parameters with no value.  Considering there are 20 selection fields on this transaction code, this does not seem like the optimal solution.  Any help is greatly appreciated.

[h_frye]

I have discovered that the users who are seeing additional selection fields pre-populated all have default user selection variants set up with the naming convention of 'U_" + username.  That explains why they fields are populated for those users, even though they aren't passed in the URL.

My issue still remains, though--I'd like to clear all the selection fields except those for those parameters that I pass in the URL.  Is there a way to do this?  Thanks in advance.