Hi,
Please use Exits or BADI to check conditions tab and give the required message.You can use the program MV45AFZZ. The appropriate exit would be USEREXIT_SAVE_DOCUMENT_PREPARE. Check the below link for available exits.
http://help.sap.com/saphelp_46c/helpdata/en/1c/f62c7dd435d1118b3f0060b03ca329/content.htm
Cheers,
Arindam