>Good idea! But a problem with such service is the queue. That means probably waiting time. Then not as quick as direct access to DLL.

Maybe, maybe not. They don't have to run on the same machine, and there doesn't have to be only one queue operator. With a proper locking mechanism (i.e. each operator changes status of a queue record to "I got this one" before it starts working on it, and then to just after it finishes) you could run several queue operators, on several machines. It's just one shared dbf.