Get Date Using Dialog Box

Hi again,

I need to present all objects that were modified within specified dates (similar functionality to what one could preform with the Find in the explorer). 

The dates should be received via a DialogBox, however I'm assuming that there is no built-in method of doing so, is that right?

If so, let's assume I provide the user with 3 DropListBoxes (month, day, year). How can I put it in one variable in the correct format? Should it include time as well? (00:00:00) would suffice. 

Thank you,

Herman