if condition and custom profile field help

[DJ29Joesph]

I have a custom profile field called steamid, I also have a custom vb page through a template and php file ( see: https://vborg.vbsupport.ru/showthread.php?t=228112) that allows members to read and purchase a subscription of a service we provide. The question I have is, using if condition, how would I have the page load but change a url at the bottom of the custom page if a condition isn't meet.

For example, click the custom page link, at the bottom, if the user has filled in his custom profile field called steamid then it allows user to continue, if he doesn't have it filled in, then change the link to edit his settings and enter his steamid in his profile.

--------------- Added [DATE]1290022431[/DATE] at [TIME]1290022431[/TIME] ---------------

In other words, whats wrong with this code:
This is for a template, not a php file.

    <vb:if condition="$post['field13']"><a href="http://blablabla.net/Forums/payments.php"><b>I want to become a Premium Member!</b></a>
    <vb:else /><a href="http://blablabla.net/Forums/profile.php?do=editprofile"><b>You need to add your steamid to your profile</b></a></vb:if>