Limit assignment of orders to one User

You can create a child table called [Sales Order Assigned To]  it will have a user field to represent who the Sales Order is Assigned to.

You would initially populate this table by a one time saved table to table import to copy all of the sales orders which have an [assigned to] into that child table.

You will then float up the assign to up to the parent sales order.  To do that you will use a combined text summary feel bad because those fields of the operate on text fields you will create a text version of the assign to field on that trail table and then roll that up using a combined text summary filled up to the sales order and then use a form of the field to convert.

OK now here's the magic.  You create a summary field for the number of assigned to use and you look that up down to the child table.  You then make a custom date a rule that says when the number of assign to's >=1, then put up an error message.  

The effect of this  that is that the second user will click to create a child assigned to  and it will fail.

And fly with a solution is that it also means that nobody would be able to edit or delete the assigned to. So we can go one step further and while I haven't tested this you could use the new UserRoles function to limit the custom data rule so that it only applies to users in the front line rules but not to the managers.

If you wanted some help implementing this you can contact me off line for some consulting time or else we could work through this slowly on this forum together.