I search the forum and google it, but i didnt find any good information, so i ask here

I am trying to learn to create process tickets, it is really cool feature and i see a lot of cases where this can be used. But i am struggeling on one thing at the moment.
I have a process called new employee and in the process i have a dynamic dropdown with all the managers. The value of the field is the CustomerID of the managers.
So in the transistion activity i want to set the customerID (TicketCustomerSet) with the value from the Dynamic field. I tried to enter the fieldname with or without the DynamicField_.
1. I think the first question should be: Am i doing it wrong or is it not possible?
2. The reason why i created this dropdown is because i dont want to the "field" CustomerID, because it should only be the department managers in that sekection. Any suggestion of how to this in another way? ACL?
Thanks in advance