Populating Dropdown Lists

Hi.  I'm fairly new to c# and .Net and I'm trying to learn this in my own time.  

On my form I have a two text boxes and one drop down list.   What I am trying to do is to populate the drop down list with the two items that are entered in the text boxes.   I'm not having much success either because I am a clueless numpty or because I need to persuade my company to pay for me to go on a decent .net course.

In the meantime, if anyone can help with a suggestion and a practical solution I would be grateful.

Thanks