Entering Revenue Contingency in an existing Invoice

Hi,

We have the following requirement.

1. Ship Confirm a SO Order Line say with USD 100.

2. Once the line comes in the AR Invoice Interface line, it needs to be split to two lines with USD 96 and USD 4.

3. Create a revenue contingency line in the contingency interface table for the line USD 4.

4. Import invoice.

What we want to know is that whether it is possible to split the line like it mentioned in the Step 2? If this cannot happen, is it possible to enter contingency records for an already imported invoice line?

Thanks

Sourav