Take a look here http://www.craigberntson.com/Articles/kb006.htm

>I have an invoice an its itens
>Both cursors are buffered as 4
>
>The ID field of the invoice_header.dbf has a relation
>with the ID of the iten.dbf
>
>I generate the ID of the invoice_header.dbf by
>
>***************************
>dimension lctemp[1]
>select max(ap.id2) from ap ;
> into array lctemp
> lcTemp[1] = nvl(lcTemp[1],0)+1
>replace ap.id2 with lctemp
>*******************************
>
>The code above is in the init event of the form
>
>Then, as itens are added :
>
>replace iten.id with invoice_heard.ID
>
>So I can see in the form, the header and its itens while they are added
>
>But this would cause problem in a network
>because the same ID could be generated
>by both operators
>
>How do you guys overcome it ?
>
>I would generate the ID only in the save method, but
>this way I would not be able to see the itens
>
>
>Moises