Adding a guestbook to users profiles

Hi, i have just created a guestbook app that lets logged in users post on the guestbook, it displays the subject, body, and the UserName of the user who posted.

Now what i wanted to do is to know how i could be able to add a guestbook on ALL users profiles, so for example, if i was logged in as User1, my guestbook link would be Guestbook.aspx?UserName={User1}

I tried QueryStrings to do this, but to no luck

I already have my guestbook code, just for someone to point me into the right direction on ow i could add the guestbook i made, and add it onto every users profile (I can post code if needed, to get a better example)

Thanks
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