Smart Template Variable with custom logic

Hi all,
How would one go about making a template variable that will only allow a certain type on input. Lets say for example I want a template variable called "Code" which must not match the code of any other resource with the same code value set. To make it a little more complicated lets also assume we would like to strip out non alpha numeric characters from a string that is entered into this "Code" template variable (sort of like what the resource alias already does I guess).

Any code examples or extras out there that do this type of thing that I can get some inspiration off?

Thanks!

This might get you started: https://forums.modx.com/index.php/topic,52539.0.html.


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Thanks for the tip BobRay, I'll follow through these threads. I thought perhpas the custom tv might be what I needed to look at.

Cheers