How to modify the breadcrumb with the previous category page

[vector17]

Hello,

I am under 1.6

A product A can be in several categories CAT1(default category for A) and CAT2

The breadcrumb will always be the same one, with the default category. : home>CAT1>A

But when I come from the CAT2 page, I would like to see : home>CAT2>A

This means that we need to check if the previously visited page is equal or not to the default category, and display this previous page instead of the default category

But I don't know how to do that...

Can someone help me on that ?

Thanks !