Validation at table level in table maintenance generator

The validation should be like we need an unique cost center in the program.

i have three fieds in the table

company code and cost center are primary fields and user is another field

The validation that we want is if we have an entry

company code          cost center            user

ww                           ARZ5511              Nithin

is allowed

it should not allow any more entry for the same cost center

ie ARZ5511

and if we have an entry

company code          cost center            user

X1                           ARZ5511              Nithin

it should not abllow any entry with

1*   ARZ5511 ttruax

  similarly for X3, X5, X7 and X9, 3*,5*,7*,9*.

Here * means the company code starting with 1.

I'm not knowing how to deal with this case.

Please help me guys.

Thanks in advance.