PhP functions with params in Templates

[temporaryins]

I'm trying to do a pretty simple set of functions. I have a seperate custom_functions.php page I've included in my template page and now I need to call a function from that in the template and use it to print out some XHTML markup with another template called as a param in the function. The function looks like:

function graphicSection ($content) {
echo('<div>');
echo($content);
echo('</div>');
}

I want to call it in the template file as:

 graphicSection($othertemplatevariable)

I don't care how the code looks really. I'd just like to be able to pass a template in as a parameter and have it print it all out. Is this even possible? What documentation do I need to look through to do this. I've looked over a lot of posts here and in the manual and can't quite find the procedures that tell me how to do this.