Currency USD not allowed for account CB-SAR-025

Hii,

In our Cash and Bank Management module we have a bank account CB-SAR-025. Its currency is SAR. 

In a transaction we want to pay from bank in USD currency. When we select currency USD and try to post it gives infolog "Currency USD not allowed for account CB-SAR-025".

Cant we post in multiple currencies?

What could be the solution?

Thanks and Regards,