configure SLA rules for context value DFF's at receipt write off lines

We have a requirement to configure SLA rules for context value DFF's at receipt write off lines. Users will populate the two of the COA segments manually at the line level when the receipt write off is created. The SLA already exist for context DFF's at the header but they want the functionality that accounting should be derived both from header or line, whichever is populated for the receipt write off.

We are using the source 'Receipt Flexfield Attribute 1' and 'Receipt Flexfield Attribute 2' in the account rule for the header level context DFF's and and attaching the account rule to the journal entry rule set of receipt write off.