Choice options

Hi all. Hope you are well.

I’m building a Case Management system using O365. I’m creating a Form that will gather initial data to launch the case.

We have a database of 22,000 employees, which is exported onto an excel spreadsheet. We also have around 300 departments.

I’d like the user to be able to select both the department and the employee by either using a set of drop downs (probably impossible) or by linking the form to a spreadsheet and using the lookup function.

Is this even possible?

Thanks in advance