How to add a foreign key check to a standard field of a table.

Hi All,

I want to add a check table for the field STKZN of the structure SI_LFA1. This structure inturn is used in table LFA1.

I am trying to do this by selecting the field and clicking on the foreign key button.

Is it right?

When I try to go in change mode for structure SI_LFA1, it asks me for Access key....

Is there any solution for this, other than entering the access key.