voucher post by business unit

Is there anyway to NOT post vouchers by specific business units ?  Changing the voucher post option at the payables definition level does not allow for posting any vouchers at all for the business unit - customers would like to enter vouchers without the checkbox in the attributes tab being checked.  Is there any other way other than setting the business unit at the payables definition level which prevents posting to the point that you can't even select the vouchers to post if you want them to.

Is there any other level to control voucher post without adding custom code behind the check box on the voucher attribute tab ?  holding the payment does not hold the voucher.  These vouchers are also entered with recorded payments - which doesn't leave much processing options at the voucher level