Exclude specific accounts from settlement from WBS to COPA

[AK37]

Hi Expert, 

I am facing the following issue. 

I have defined a settlement rule in order to settle costs from WBS to COPA (PSG). In my allocations I want to exclude some costs that has to remain in WBS. 

So I created a Allocation Structure and Source Structure not filling the defined Accounts but when I try to execute the allocation through CJ88 I have the following error:

"Complete Source Structure ZP". 

If I fill the Account in the Source Structure leaving it from PA Transfer Structure I face the following error:

"Complete PA Transfer Structure Z1".

Could you help me?

Thanks

Armando