Hi Tamil,
Looks like you will have to store the actual agent determined initially when a process level is evaluated. You can add extra custom field "ACTUAL_AGTS" in the Shopping Cart header and fill it with the actual agents determined via BADI.
Add custom field to SC and POWL
Now if the approval item is forwarded or substituted (say to current agents) then this custom field still has the reference of actual agents. In your process level evaluation code, you can check if the previous approver (actual agents) is same as current then dont trigger the level.
To check Substitution of current user, you can query table HRUS_D2 for validation.
Hope it helps
Regards
Sandy