>I have a combo, .Style = 0-dropdown combo, .RowSourceType = 1-Value, Rowsource = TBD,N/A,VARIOUS, ControlSource = mytable.myfield. I thought that .Style = 0 meant that I could enter anything in the control, but it's not showing what I type, unless I select or type one of the three values in Rowsource. Since, for testing purposes, I have left in an old textbox with the same controlsource, I can see that values other than these three are not being saved to the table. What's going on?

I guess, the problem originated from ControlSource. Personally, I don't use this property at all. Basically, combo will work this way:
Combo.Lostfocus event:
if this.dispalyvalue<>this.value
This.additem(this.displayvalue)
endif
Use Value property when you "Save" the record to fill appropriate field.