Yes, it is possible to automatically insert the user name (login name) in Excel. Here are the steps to do it:

1. Open the Excel document where you want to insert the user name.
2. Click on the "Insert" tab in the ribbon menu.
3. Click on "Header & Footer" in the "Text" group.
4. In the "Header & Footer Tools" tab that appears, click on "Design".
5. Click on "Quick Parts" in the "Header & Footer Elements" group.
6. Select "Document Property" from the drop-down menu.
7. Select "Author" from the list of document properties.
8. The user name (login name) will now be inserted into the header or footer of the document.

To make this process automatic for all 40 users, you can create a template with the above steps already completed. Then, each user can simply open the template and their user name will be automatically inserted into the header or footer.