aruefer
You can paste values by selecting the rows you want and then pressing control (or command on Mac) + v. Pasting into the internal standards table will paste into the values column of the selected rows.
It seems when you copy from Excel it adds in a blank line at the end of the copied text which causes an error when pasting. If you bring up the python console in iolite, you'll probably see "ValueError: could not convert string to float" or similar. I've fixed this now for future releases, but in the meantime, you could paste the copied text into a plain text editor and then copy just the values from that without the blank line at the end.
All the best,