Hello! I am overriding the standard Opportunity Product selection page. I have two custom fields, Effective Date and Expiration Date, on this page. My users would shower me with gifts and praise if I could implement functionality that would auto-populate all Product Effective and Expiration Date fields based upon the selection they make in the first Product row (see this image for clarification).

I know this will require Javascript, which I know next to nothing about. Hopefully, since I am already overriding the page with Visualforce, someone can provide a Javascript code snippet that I can easily paste in to at least get started? Thanks for any help!

I have two  fiellds on object   Colors    ,   Rejection Reason

Colors is MULTISELECT picklist

Rejection Reason  is just a picklist 

Whenever the colors B,C,D,E,F,G  in any combination are selected  Rejection Reason field is mandatory

Whenever the color A is selected Rejection Reason is not mandatory

Whenever the color A is selected along with B,C,D,E,F,G   (any combination as it is a multi select picklist )  Rejection Reason is not mandatory

Colors has the following values                                                    

A, B ,C ,D,E,F,G ,H      

I am able to get through all scenarios except the third  

Can anybody please be a life saver for me