teaser count with different node type

Ok now. Here is my situation. I have the node types of "story" and "blog". I want to have teaser for story node only but not for blog. I know I can set the length of the teaser at administer -> setting -> posts but it will trim all the node types only.

Let's say is it possible to make something like:

"Story" node -> Length of trimmed post = 200 characters
"Blog" node -> Lenght of trimmed post = Unlimited

Can someone tell me how to set the length for a specific node only?