How do I copy a Word document range to another document without using the clipboard ?

I'm using c# and Ms-Word.

I want to copy paste a Word range for one document to the other.

Range.Copy and Range.Paste use the Clipboard.
This is not acceptable if the User makes a manula copy/paste while the programe is running  in the background.

How do I proceed to copy/paste ranges without using the clipboard.

I tired "myDestRange.FormattedText=mySourceRange.FormattedText". But this triggers an error "wrong argument" like.

any idea ?