OK, first I created two chunks, {{Loginmenu}} and {{nextGroupCheck}}.
{{Loginmenu}}
<h2>Main</h2>
<ul>
<li><a href="http://www.site.com/">Home</a></li>
<li>[+phx:mo=`Vendors`:then=`<a href="[~40~]">My Account</a>`:else=`{{nextGroupCheck}}`+]</li>
<li><a href="[~43~]">Brides</a></li>
<li><a href="[~1~]">Calendar</a></li>
<li><a href="[~30~]">FAQ</a></li>
</ul>
{{nextGroupCheck}}
[+phx:mo=`Registered Members`:then=`<a href="[~5~]">My Account</a>`:else=`<a href="[~2~]">Login</a>`+]
I then placed {{Loginmenu}} in my template where I want the menu to appear.
The logic works like this. When the {{Loginmenu}} chunk is called, the first PHx test is run:
Is the user a member of group Vendors?
Yes - display <a href="[~40~]">My Account</a>
No - display {{nextGroupCheck}} chunk
If the test returns No, the {{nextGroupCheck}} chunk is called and the second PHx test is run:
Is the user a member of group Registered Members?
Yes - display <a href="[~5~]">My Account</a>
No - display <a href="[~2~]">Login</a>
In which case, only one link will be displayed. Does this make sense?