simple pull down menu

I have a little script I wrote for processing a job folder that I run every time I want to add a project into my “jobs in process” folder so that they get properly named with job number, client name, job name, and have empty folders inside with consistent naming and such. Right now it just has me enter the client name - I’d like to have a text field there with an integrated pull down so I can enter as I do know, or I can pull it down to add in client names for our typical high-volume recurring clients to avoid a few keystrokes and to keep naming consistent - sometimes I forget how I abbreviated something the time before or what words I left in or took out (inc, company, etc.). I have very little scripting knowledge, just dabbling. Any assistance would be greatly appreciated.

Model: Mac Pro (early 2009)
AppleScript: 2.6.1
Browser: Firefox 28.0
Operating System: Mac OS X (10.8)

What you want is a combobox.
Take a peek at Pashua. From its manual: 'Pashua is a tool for creating native Aqua dialog windows on Mac OS X’.
You can drive it with plain AppleScript, and a whole lot of other languages.