There is a combo box (dropdown list) with a list of revenue types. If the user types into the box a value that is not part of the list, a msgBox pops up and asks them if they want to add that value to the list.
Here is my problem: In that msg box, I want to give the user a combo box list of revenue groups to choose from (so that the essence of the dialog is "oh, you want to add a new revenue type. Now pick which revenue group it's from).
Is there any way to add a combo box to a msgBox?
No, there is not. The usual solution is to build a small form and use that as a dialog.
DoCmd.OpenForm "TheCustomFormName",acNormal,,,,acDialog
You might want to try out Arvin Meyer's MsgBox replacement form:
http://www.datastrat.com/Download/MsgBox2K.zip
I've never used it, but Arvin's an Access guru of long standing.
For what it's worth, what you describe is a dialog, not a message box, so in that case, I'd design a custom dialog form.
Dmitri Furman also has a MsgBox replacement:
http://iridule.net/cu/files/mboxfunction.zip
...but his sounds like a more straightforward replacement, and likely not helpful for your situation. I include the link just for completeness.