Drag an object on the Y-Axis only

I'm making a training for some software and I'm trying to mock-up the application's interface.  One of the things is a drop down list of numbers and I want my user to be able to drag the list up and down.  

Is there a way to take an object, be able to click and drag it just on the y-axis, and to limit how far up you can drag it and how far down you can drag it?  

Thanks.