How to get actual value of package method parameters of the call stack?

 Hi,
I wrote some procedure to display the current call stack when invoked at any given point in PL/SQL using DBMS_UTILITY.FORMAT_CALL_STACK and dba_source.

It produces output like this:

<no timestamp>    ******************* Call Stack Begin ******************
<no timestamp>    ANONYMOUS BLOCK:
<no timestamp>         BEGIN IFSAPP.INVENTORY_PART_API.MODIFY__( :a,
<no timestamp>          :b,
<no timestamp>          :c,
<no timestamp>          :d,
<no timestamp>          :e ); END;
<no timestamp>         Bind variables:
<no timestamp>              A =
<no timestamp>              B = AAAPBRAAFAAAFUcAAA
<no timestamp>              C = 20091028192731
<no timestamp>              D = PLANNER_BUYER|JOPAE|
<no timestamp>              E = DO
<no timestamp>    INVENTORY_PART_API.Modify__ - 3195:
<no timestamp>         Unpack_Check_Update___(attr_, newrec_, objid_, TRUE);