Replace 'fieldXX' with your user profile field field number (ie: 'field20')
Insert your widget HTML code
Find and Replace all instances of your last.fm username used to create the widget with your user profile field id variable (ie: ?url=user%2FHENRY should become ?url=user%2F$post[fieldXX]) - bold is only for looks. ^.^
Close the table with the following (tweak code according to style):