I have a form with a series of text boxes for entering order information. But 
because i want to be able to select more than one entry from a combo box, I 
thought it would be nice to have each item added to a text box and for 
neatness and ease of programmability, I'd like it if a combo box would pop up 
beside the text box much like the date picker pops up when entering a date 
field. Then each item selected could get appended to what's already in the 
text box.

So my questions are:

Does such a thing already exist and i can just download it and add it to my 
database?

or

Is there sample code of how the date picker works so that I can examine it 
and attempt to adapt it  to my DB

Thank you!