Setting up PO Approvals in BPM with a condition related to Change Orders

Summary:

Hi,

We have a requirement as below:

If Change Order exists on PO and Change Order Amount < Ordered Amount then route to Approver A

If Change Order exists on PO and Change Order Amount > Ordered Amount then route to Approver B

If Change Order not exists on PO then route to Approver C

I am trying to use below rule for condition 1:

PurchasingDocumentHeader.isChangeOrder is "Yes" and

PurchasingDocumentHeader.documentCurrencyDocTotalChange is less than PurchasingDocumentHeader.documentCurrencyOrdered

Approval - Approver A

below rule for condition 3:

PurchasingDocumentHeader.isChangeOrder is "No"

Approval - Approver C

But it is not working, it is not identifying the Change Order and change Amount. Could you please help the condition in this case.