sure..
1 way to do it is to hijaack 2 extra fields
1st one is yes/no for public/private
2nd one is the actual value
other way to do it is to combine them into one ( if you don't want to kill 2 extras )
so for example:
1,Weight Goal: 125lb ( shows )
0,Weight Goal: 125lb ( hidden )
then post_side.tpl, post_top.tpl could display, with the heavy lifting done by showflat.inc.php