Master/Detail Problems

Hello there,

I have got a little big problem...

I'm using Delphi 3 in order to make a database which is using a Master
table and Detail table. So far so good. That works wonderfully !
Both tables are linked via a secondary index in the detail table and is
sorted by a primary index.

Now, each time I try to write into the field being the index when
appending a new record I get the exception : " Index is write protected

It is very important do create a new record within this detail table in
order to link let's say orders to the company in the master table.

Pls help,

Many thanks and greetings from Germany!