Stopping sequence increments

[Quoted] [Quoted] Can anyone explain why and suggest a remedy for the following:

In my master-detail form (Forms 4.5) where master block is query-only, detail block has a Primary Key field generated by a sequence.

Why does the detail block generate a new record and thus increment the sequence for every new query on the master block. (many of the master records have no corresponding details).

Have I missed some simple property setting ?

Thanks in advance for any advice.

-- 
Mark