How to lock Excel files and prevent two people from editing them at once?

Hi pleasehelpme1 - welcome to our Community!

I'm sorry to hear you're having issues with this. Let's have a further look into it now!

First off, note that conflicted copies can indeed occur when a file is left open on another computer (or by another user), especially when using applications with an auto-save feature. Closing the file from within the application on either computer should prevent further conflicts.

One workaround that can be used to prevent conflicted copies is to move the file out of the Dropbox folder while editing it. Doing this causes the file to appear as deleted and doesn't allow other users to edit the file. Once you're done editing, you can move the file back into its original location in the Dropbox folder. It will reappear with your edits for all users who have access to that file.

Another thing you could consider in this case, is using the Dropbox Badge as it will let you know that others are editing the file by turning red and displaying a lock icon. You’ll still be able to edit, but the badge is there to warn you that if you and the other person continue editing at the same time, you may create different versions of the file.

I hope this information helps and please keep me posted on your progress!