Plugin via an external PHP

[Dr.CustUmz]

i've dug up about all i can find on using external php files within vb. they all turn up to be something like this HERE

thats not exactly what im trying to accomplish here though.

so i have an xml, within it i have my plugins and all the PHP for the plugins the one i particularly want to include externally is a misc_start plugin that looks a little like:

<plugin active="1" executionorder="5">
			<title>DRC - Secret - Project - Misc</title>
			<hookname>misc_start</hookname>
			<phpcode><![CDATA[
A WHOLE LOT OF PHP
			]]></phpcode>
	</plugin>

i want to be able to just put all that php into an actual php file the user can upload, then call it from within the xml or something... is there how exactly would i go about that =/

or would i still be doing the same thing as shown in the link at the top? even though this is not a template...