I have one Excel Workbook with 3 tabs. In each tab there is a column with customers names.
How to make a multi-select ListBox on a Form that contains unique values from all 3 tabs at once?

So I do not want to have unique values from tab A + unique values from tab B + unique values from tab C because still I could have duplicates accross all 3 tabs. Is there a built-in function to solve this?