Backend: Turning on or off an ad or link

Is there a way to make either a checkbox or dropdown in the manger that will allow you to turn something on or off,

e.g.: [htmlstuff1a] [ad1url] [htmlstuff1b] [ad1] [htmlstuffc]
<a href" URL "><img src="[ad1] " alt="" />
Where the above has a check box to enable htmlstuff1a/b, making it <a href"[ad1url]">

Basically I want to have to ability to enable and disable an ad on a page. If you need more information please let me know.
I know it is kinda complex and confusing but to improve the visual quality when there are no ads running I’d like to have the option to turn them off.

Thanks, but could you give me an example, I’m having trouble understanding it the way you put it.
Thanks in advance.

I’ve been using modx for awhile and I have used may TVs, but I don’t understand what you mean by "If you want to turn the ads off, just leave the textfield of the top-most document empty."

www.rockin8.com/index.php?id=38 is the page I am trying to toggle ads on. They currently want to have the ads turned off when the template goes live, but want the option to have ads turned on later.

I tried using the @Document and for some reason the page doesn’t get loaded into my template. The code doesn’t even show up in the source. I don’t know if I have something wrong or what.