How to make attachment mandatory using on change client script.

[dhineshkumar]

Hi Experts

I have the catalog item, I want to make the attachment mandatory with condition of select box, If I select YES option. If select No attachment should not be mandatory Please help me on this.

Thank you.

[dhineshkumar]

Its not working 

[dhineshkumar]

How to add the script include, Please help on this. bit urgent  ??