It would help if you attached a sample Excel workbook.

To do this, click on Go Advanced (below the Edit Window) while you are composing a reply, then scroll down to and click on Manage Attachments and the Upload window will open. Click on Browse and navigate to (and double-click) the file icon that you want to attach, then click on Upload and then on Close this Window to return to the Edit window. When you have finished composing your post, click on Submit Post.

Please note that the Paperclip icon does not work.

This:

... IF(3500>E20>=2000; ...

is not a valid Excel expression. You have already tested for E20>=3500, so you don't need to test for it again.

Hope this helps.

Pete