Suggestion on Purchase Requisition Approvals

Hello,

Need one quick help.

We are implementing AME for Purchase Requisition Approvals. Here are 2 requirements: 

1) For Purchase Requisitions where 'Destination Type' is 'Expense', approval list should be built using AME based on approval limit of requester. -->This has been taken care of and is working fine.

2) For Purchase Requisitions where 'Destination Type' is 'Inventory', the preparer of the requisition should be able to approve the document. No additional approval required. --> While working on this requirement, we tried to build a rule which will check the Destination type. If it is 'Inventory' then we are building an approval group which returns the 'Preparer' of the requisition. This is where the problem starts. Because of this rule the preparer has to approve the 'Inventory' type Purchase Requisition