Puzzled about a coordinated task sequence, please help

Ladies and Gentlemen,

I have ran into a situation which I managed to avoid so far and unsure how to proceed.

I have a team of m operators connected to a dispatcher, and a park of n vehicles, connected to another dispatcher.

I want my task sequence to allocate one operator, wait until the vehicle becomes available, then perform a number of subtasks involving the following steps:
* operator allocates the vehicle
* operator walks to where the allocated vehicle is parked,
* operator enters the vehicle,
* vehicle drives to a queue,
* operator exits from the vehicle,
* operator loads flowitems from the queue into the vehicle,
* operator gets back into the vehicle
* vehicle drives to another queue
* operator exits the vehicle
* operator unloads flowitems from the vehicle into the queue
* operator enters the vehicle
* vehicle drives to the designated parking sport
* operator exits the vehicle
* operator walks to his designated station, which concludes the task sequence.
The problem is that some of those subtasks I want to be coordinated task sequences between the operator and the vehicle. So I can create a subtask for one, for another, but never for both of them (as I understand it, because when I am calling TASKTYPE_CALLSUBTASK for one, the other one is already allocated and cannot be allocated again in the subtask at the same time). It would have worked if I were to allocate the vehicle anew for each subtask, but then another op could steal it.
The annoying part is that I am not even getting an error message - when I comment out allocation for the vehicle, the remaining part works, but when I uncomment insertallocatetask(), the whole subtask silently fails to execute without any kind of error message.
What is the correct way to approach such situation?

I suspect I can solve that by creating a task assignment routine in the vehicle dispatcher that won't let me allocate the vehicle for another task as long as some kind of flag is set so that when the op tries to allocate the vehicle in each respective subtask he will always get the same vehicle, but it seems hacky. Is there a better way?

Thanks!
Vadim

Ladies and Gentlemen,
I am happy to inform you that the problem has been solved:

Instead of connecting the vehicles to the dispatcher, I connected the equal number of BasicTE proxies, which, in turn are connected to vehicles via center-links. I simply allocate the proxy at the beginning of the task and release it at the end. For each CALLSUBTASK I allocate a centerobject of the allocated proxy and release it at the end of the subtask, because I am assured that as long as the proxy is allocated, the associated centerobject will remain available.
The downside, of course, is doubling the number of TaskExecutors in the model, so, if someone has a better solution, please post it.

Dear Fooks,
Can you please upload a sample model of your solution for better understanding.
Manoj.