[Ted S]

Well since you were so polite here's some [untested] code...

<if condition="(($bbuserinfo['joindate'] - (86400 * 30)) < TIMENOW) AND !is_member_of($bbuserinfo, X)">
Message Goes Here
</if>
<if condition="$welcomehdr = '1'"></if>

Open the existing template welcome_headers and find:

<if condition="$vboptions[wlhguest] AND $show['guest']">

Place this code above that line and change the line to:

<if condition="$vboptions[wlhguest] AND $show['guest'] AND !$welcomehdr">

Change X to the supporting member group or enter a list of groups like 1,2,3,4 to have the message not show for multiple supporting options, mods, admins, etc...

Change 30 to the number of days.

Let me know if you run into issues. Be sure to test!