"The External Bank Account Already Exists"

Today is my day for unusual issues cropping up.  We have a husband and wife who both work for us, have a joint bank account that they boh would like to have their expense report reimbursements electronically deposited to.  However, since they are separate vendors, when I try to add the bank account to the second party, I get the error above.  Anyone know of a workaround for this?  As always any assistance is greatly appreciated.