link between purchase order and asset using wbs

Hi,

we have this scenario:

1. PO we give WBS element

2. After migo balance goes to WBS

3. After that we settle this WBS to AUC

4. Latter we settle this AUC to some fixed asset

5. Now we want some link or functional module which give me link fixed asset to PO/MIGO  used in the settlement.

How we can get that??

Thanks