Custom BB code translated by plug-in

[ShayA]

How do I add a custom BB code that will be translated by a plug-in:

I will define a new custom BB code, name it as [PHOTO].
Suppose that in the editor I will write [PHOTO]http://www.123.com/p.php?if=100[/PHOTO]

I would like to have a plug-in that will be run for every [PHOTO] BB code. That plug-in will get the [PHOTO] BB code staring value and will return a string that will be placed instead.

How this can be done.

Thanks,

[Borgs8472]

Replacement variables?

[ShayA]

What do you mean ?

[Princeton]

<a href="http://www.vbulletin.com/docs/html/style_replacement" target="_blank">vBulletin Manual - Replacement Variable</a>

[ShayA]

no.... the replacement variable option will not be good in this case.
I need to be able to get the variable from a custom BB code then to use it as a parameter to a custom function that I will write (using plug-in) then the return value from that function will be placed instead.

How this can be done?