A quick answer
This will copy ' --TEXTSTRING-- ' to the clipboard and you can then paste to a spreadsheet from there, this is perhaps the simplest solution though having to manually paste to excel add a little work (can also paste to wherever you want with this, a text editor, word processor, another drawing or wherever.
CAD is off today, Sunday, but I think if you create your text string with a tab character in between 'cells' it might paste them into new cells - not something I have done though. Not sure about multiple lines.
(vlax-invoke (vlax-get (vlax-get (vlax-create-object "htmlfile") 'ParentWindow) 'ClipBoardData) 'setData "TEXT" --TEXTSTRING-- )
You could also look at 'paste special' in excel, s there an option to paste CSV (comma separated values), and in that case you can create a temporary CSV file and paste that?
Working with spreadsheets via AutoCAD.... a but tricky I understand but if you can save your text as a half way, like CSV it become a little easier but you need to do more work.