I just used the same exact code you have listed above MsgBox Me.Combo.Column(1)
Something is wrong with one of the following:
- Your control is not named
Combo
- You do not have a value picked in the combobox
- Or you record source for the combobox is not returning any results.
Please post the combobox recordsource. If you provide more information, I can assist you better but those are the most common problems with invalid use of null with comboboxs
EDIT
I noticed in your code that you have Me.Combo.Column(1)
and it should be Me.Combo.Column(0)
since you only have 1 column it is a zero based index. Additionally, I would create that code within the vba for that form. If you click on that combo-> properties-> event tab-> Afterupdate -> ... -> codebuilder and add your code there, it will do whatever after you update the combo box.