Adding a site-wide template variable.

[neverstop]

Hi,

I am looking to add a template variable that will be usable in all templates. The variable will be an integer between 1-9 that will be random on each page load. I want to use this for site wide "advert page-skinning" for lack of a better term.

Basically i want to be able to add something like this to any template:

<vb:if condition="$integer == 3">fu</vb:if>

or

<vb:if condition="$integer > 5">fu</vb:if>

or 

<vb:if condition="in_array($integer, array(4,8,9))">fu</vb:if>

Something like this should be fairly simple via a plugin no?

Thanks in advance.