I need to edit the "add image" function

Hello! I am new to fck
It works great, and it's pretty simple to make it work.. well maybe it works TOO MUCH
In fact I need to limit the add image functions to just let someone put in the link of the image he wishes to post.
Was I clear?

I mean: I just need someone to post images hosted somewhere else, so that this someone may only write a link when clicking on add image.
Is it anyhow possible? Pwease help me

Ed from Italy