Posting invoice to an alternate contract account

Dear SAP Gurus,

My client has a requirement that invoices generated from a certain contract account should be posted to an alternate contract account

So for eg There is a Contract Account 123 with contract 220. The client wants that any invoice created against contract 220 should post in another Contract account 124 and not in account 123

Pls suggest any way of achieving this. Would appreciate

Thanks!