This suggestion will put the next tech in line at the top of the list, and depending on your table relationships you can make it conditional so it only shows the techs that are assigned to that office.
I'm hoping you have a set up similar to this: (One --> Many)
Office --> Techs
Office --> Issues
Techs --> Issues
If that's the case you can make the tech dropdown conditional upon the office.
Additionally, you can summarize the "Maximum Issue Record ID#" back to the Tech table, then use that number to sort your techs, so somebody that's had an issue later in the sequence will have a larger number, thus being at the bottom of the list. So you just pick they Tech at the top of the list.
