Relation problem

[Spiet]

How can I solve this problem? I have One table named Company with a comanyID. This company has more memo's and persons. So I have a table Memo with MemoID and companyID and a table persons with personID and comanyID. When I link both tables memo and persons to the table Campany companyID. It doen's work. It only works if I create a relation to one table memo or persons and not both! Can anybody help me out?

Thanks