>
> Is there some way of taking over a file exclusively
> that someone else is already using non exclusively over a Network?
>

As the others stated exclusive means "exclusive". The question however is why do You want to use it exclusively?

The only things that come to my mind where You really do need are Data Reorg (like reindexing or packing) and maybe Backup. In both cases You'd better really DO have exclusive access and do not really want others to modify ANYTHING during the job.

I think anything else can be done in shared mode properly. However certain projects sometimes have special demands or constraints.