calling a JavaScript function on status change event in opportunity form

Hello All,

I am calling a JavaScript function on status change event in opportunity form.

Here, I am trying to set a custom option set field value using below code.

  Xrm.Page.getAttribute("CustomOptionSet").setValue(1);

Its not showing with new assigned value,please suggest why its not working.

scenario:
Once,I am Reopen opportunity I need to set option set value.