No. It may be possible to use the AfterUpdate event of the text box to parse
the address from the HyperlinkPart(), and Replace() the prefix.

However, there are so many possible things that could go in a hyperlink -
web pages, email, ftp, news, local files, server files, and in the future
things that do not even exist when you created your database - that this
seems like a dicey way to go. It is probably better to just use a Text field
instead of a hyperlink. You can make it look and behave like a text box by
setting the properties of the text box on your form, e.g. using DblClick
event to SendObject.

Tony Toews has a good Email FAQ, so if you are looking at other
alternatives, see:
   http://www.granite.ab.ca/access/email.htm