Invoice line does not inserted into job ledger entry table

Dear friends,

This is about job module in NAV 2009 R2. So my user create an Purchase order for job and follow the process until it posted as posted purchase invoice, because he used a wrong purchase price for that particular PO so we asked him to create the credit memo.

After create the credit memo, he created a new PO (with job no. on it) and follow the process until it posted as posted purchase invoice, at first I thought there is no problem with it, but it turns out that the new posted purchase invoice line does not inserted into job ledger entry table.

I look into the value entry table for the new Posted Purchase Invoice and find out that the value of Item Ledger Entry No. used by the new Posted Purchase Invoice is the one that used by the old one.

am I doing a wrong process ? does anyone have this problem before?

Thanks,

Yosa