I am using what you call a multiselect combo box. The multiselect combo box allows me to select multiple items simultaneously, which are stored in a multivalue field in a table. Yes, multiple items, each separated by a semicolon, saved in the same field, based on a list of possible values contained in a Lookup Table each with a text value and a corresponding numerical key value that is actually saved. That means multiple key values saved in the same field, appearing to be separated by a semicolon, but only editable through the check marks in the combo box, either through the combo box I am using on the form, or the combo box that is built into tables specifically for multivalue fields, both combo boxes containing check boxes for each value to allow multiselect. Microsoft calls such fields multivalue fields, so I used that word, but since you think that does not mean multiselect, let me be clear that it is possible to select multiple items in the combo box and store these multiple values in what Microsoft calls a multivalue field. If you look at my other thread I was also wondering how to determine whether the multiple items selected in one multivalue field are a subset of another.
It appears both of you did not understand the question, so maybe now somebody can give a proper answer.