Standard Memo Lines vs Cross Validation Rules

Summary

Standard Memo Lines in billing default to acquire Customer Code into GL code

Content

Standard Memo Lines in AR Transactions (invoices and credits) default to acquire the Customer Code part of the GL code string from the customer being billed.  They can be manually changed one-by-one when the transaction is being created.

A number of our Standard Memo Lines post to Balance Sheet accounts (various deposits by the customer).

But our Cross-Validation Rules require the Customer Code for all BS accounts to be 000000000.

Can I specify the Customer Code 000000000 for some (but not all) Standard Memo Lines to override the Customer Code of the customer being billed?