Create/define a parameter just like you do in a catpart. When you assign a value to the parameter, do it as a function, go to the catpart and select the parameter, material, etc. that you wish the value to be. You will then have an external parameter set up that can be synchronized to maintain updates.
Many thanks for the post, other forums had lead me to believe that this functionality was not available in Catia V5. As a former Pro/E user I found that quite frustrating.
But I am struggling a bit, I am having trouble creating the parameter as a function in drawing mode, can you give me detailed instructions
If you already have your parameter created:
1) Open the parameter by double clicking on it
2) right click in the value area box
3) On the contextual menu, select Edit formula. This will bring up the formula box.
4) When the formula box appears, you can insert differnt equations, or you can go to the catpart, and select the parameter from there. Since you want material properites. Select the material in the catpart. From there, you can choose what you want from the part definition.