Welcome Message help

[bubbasmurf]

What I'm trying to do is set this up so if a user hasnt posted in a number of days it will show a message from the welcome_postmoreoften phrase list but am having problems getting this to work.
I put this in the FORUMHOME template and I have tried everything I can think of but just can not get this to work. Can any one help please?

<if condition="$headerstime - 1209600 > $bbuserinfo[lastpost]">
<!-- never posted message -->
<br />
<table class="tborder" cellpadding="$stylevar[cellpadding]" cellspacing="$stylevar[cellspacing]" border="0" width="100%" align="center">
<thead>
<tr>
<td class="alt1" colspan="6">
<phrase 1="$bbuserinfo[username]">$vbphrase[welcome_postmoreoften]</phrase>

</td>
</tr>
</thead>
</table>
<!-- / never posted message -->