Check table entry does not exist

I have a a header table and corresponding item table

key fields of my header table are

name domain

contract_no vbeln

kunnr kunnr

key fields of item table are

name domain

contract_no vbeln

kunnr kunnr

posnr posnr

Here i have made the fields contract_no , kunnr of header as foreign key to the item table. I have created the header table entries and then the corresponding entries in the item table .

Now my problem here is I have a screen element I/O element which refers to the item table contract no... when i do an f4 on the screen field , select the existing record and press f8 then a system error is shown saying the check table entry doesnt exist in the header table

Could any one of you please tell me what the problem is??

Regards,

Aruna