Crystal Reports - Pulling List from DB

Hi all.

I have a report that was designed for a service dispatch application. I have a field called "ServiceType" that has the following information:

Drive Up Systems
Alarms
Vault Doors
Vaults
(etc).

Now, this list stays pretty constant. However it can change. I was able to set a "default" list for the user to choose from based upon the data field. What I would like to do is to create a drop-down list for the user to choose from that refreshes from the database field everytime the report is run. This list would be the part of the criteria for the report.

Any help would be greatly appreciated.

Thanks in advance.