Insert your emotication first,
Click on box at bottom of message that says "Use HTML to create your page" which is right under the reply box....
You see your post changed to these:
<DIV><IMG height=19 src="http://sc.groups.msn.com/themes/R9c/pby/img/emoticons/emsmiled.gif" width=19></DIV>
Right after <IMG hit the space bar then type title="Oh..I see!" or whatever message you want
Now it should read like this
<DIV> <IMG title="Oh..I see!" height=19 src="http://sc.groups.msn.com/themes/R9c/pby/img/emoticons/emsmiled.gif" width=19></DIV>
Then you uncheck the "Use HTML to create your page" box, you get back to normal page showing your emoticon/ smiley face....then hit send in normal way, and your should see the hidden message you wrote