Unfortunately it needs to be an excel file with multiple sheets.
I found a workaround on cadforum.cz for windows clipboard without using vlax-create-object, but I have no idea if that would work for excel and how to change it:
(setq cltext "Hello world!")
(startapp (strcat "mshta.exe vbscript:close(CreateObject(\"WScript.Shell\").Exec(\"clip\").stdIn.WriteLine(\"" cltext "\"))"))
Is anyone familiar with this kind of code?