Help with Pop-Up Icon on Message Post

[dsincos]

Hi all -- my first post on the forum here! 

Basically, what I'm looking to do is have users be able to insert an image through a popup that is elsewhere on my site.

So, the user will click a button on the message post page, which will run a JavaScript function to bring up a popup window. Then, the user will choose a picture, and the code inserts it into the "message" textfield element on the parent page within [img] tags.

I've tested that on a separate page and everything is working just fine.

But here is where I'm running into trouble: where can I edit some SMF code that I can insert my HTML/JavaScript for a button to open the popup? I'm fine to have it as one of the BBCode buttons and create one of those, but I'd also be fine with just having the button as a separate element by itself between the Smileys and the textfield for the message -- whichever is less complicated to create.

If anybody can help me get started on how I can insert some custom HTML into the post page, I'd greatly appreciate it!

Thank you in advance!

[Colin]

The file you are looking for is post.template.php. Is that all you were looking for or are you still unsure where to place the code within that file?