I have a scanner without multiscanning, so I have to do it manually. The problem is how do I eliminate extreme values when averaging?

Let's say 4 scans result in following values for a point: 123, 125, 127 and 250. Obviously, 250 is a fluke and this spike should be eliminated before averaging out the first three values.

Question: How do I do this in Photoshop 6? Layering the 4 images with opacity of 50%, 33% & 25% would include the extreme value.

Thanks!

Don.