I've done another update to the Data Validation Multiple Selection sample, thanks to a question from Pat, in a blog comment. He has 3 columns with different drop down lists, and wants to add new items to the applicable lists.
I can get 3 separate columns to each allow multiple selects from their own lists and to allow write in contents...But what I want ...is to make the selected columns (not all) so that write in selections are written to the lists and the lists are sorted.
So, in the new example, on the SameCellAddSort worksheet in the sample workbook, that's what happens. You can do a multiple select in columns C and D, but only a single selection in column B.
Add New Items
New items can be added to the Names and Numbers columns. If a new name is entered in column C, is will be added to the NameList range on the Lists sheet. Then, the list is sorted alphabetically.
Download the Sample File
To see the code, you can download the Data Validation Multiple Select sample file. The file is in Excel 2003 format and zipped. There are macros in the file, so enable them when opening the workbook.
Watch the Multiple Selection Add Sort Video
To see how the multiple selection add and sort technique works, and see an explanation of the code, you can watch this Excel video tutorial.
Or watch the video on YouTube: Data Validation Multiple Selection Add Sort
More Information on Data Validation Multiple Selection
Most of the examples in the DataValMultiSelect file have limits set in the code. For example, the code might check the column number, and only allow the multiple selections if the column number is 3.
If you remove those checks from the code, and just check for data validation in the selected cell, you could have several multi-selection lists on the same worksheet. There is an explanation on my Contextures website, for adjusting the code:
Excel Data Validation - Select Multiple Items
Here are a few more article on the data validation multiple selection technique:
How to Set up Multiple Selection Excel Drop Down
Edit Multiple Selections in Excel Drop Down Lists
Select Multiple Items from Excel Data Validation List