List Box with NULL option

[RawToast]

I have a table for holding client responses to a questionnaire. 10 of the fields in this table are List Boxes with options "Yes", "No", and "Blank/Other". The "Blank/Other" option is supposed to be reserved for forms handed in where the field has been intentionally left blank. If the form has not been handed in at all, I want the fields to just be NULL. The problem is that if someone accidentally fills out information for a row that should all be NULL, there is no way to correct it. I have tried adding NULL (no quotations) as an option in the list box, but this does not work. I have also tried adding "" as an option, but no luck there either.

tl;dr: How do I add an option in a list box to leave a field NULL?

[orange]

You can try this link for ideas.

Let us know if any of the ideas/suggestions work for you.
Good luck.

[RawToast]

You can try this link for ideas.

Let us know if any of the ideas/suggestions work for you.
Good luck.

Thank you for the reply. Unfortunately, I was not able to find a solution in the thread you shared. I would rather not have to have users use a VBA script in order to make a field NULL. I am looking for a way to add a NULL option to the List Box, but I do not know what to enter in the Row Source in order to accomplish this.

[orange]

You may want to research what NULL is. To start see http://databases.about.com/cs/sql/a/aa042803a.htm

[June7]

Users can select the saved value and Delete.

Is the combobox RowSource a Value List? I don't see any way to force Null as a Value List item.