I've never done it with vc++ but I've done it with vb several so I know the process of getting it done.
First off you need to get the data from the database that you want to show on the form. First connect to the server. When you connect you save a handle in a variable, usually conn or something similar so you know that that is your connection to the database. With this variable you would need to run an SQL statement to get the data you want. When you get the data you want, it will be stored in what is called a recordset. You then process the recordset sort of like an array, only instead of cells and indexing it like an array, you move from one record to the next with a command like recordset.movenext(); As you move through each record, add it to the combo box.
You would need to complete this process for each combo box.
Another way to do this would be to link the box directly to the combo box. This method is not as powerful as the SQL version, and I'm not sure anymore how to do it, but I know it is possible, or it is in vb anyways.
Hope this helps, if you have anymore questions, feel free to post back.