help writing simple plugin

[aebstract]

Essentially I just want to do this:

$result = mysql_query("SELECT COUNT userid FROM userban WHERE adminid = '1'") or die(mysql_error());
while($r=mysql_fetch_array($result)) {
$var = "$r['userid']";
}

and be able to use the variable $var in my template where needed. I'm lost at how I'm suppose to do it since I don't understand hooks that much and am unsure how to code geared for a plugin.