How to set a URL attribute of WTPartUsageLink?

Hi,

I have a soft attribute (URL) for WTPartUsageLink called LabelControl.

Under the Uses tab of Structure tab of a WTPart, I want to be able to set a URL based on the label entered in the URL Label  field.

The label will be the name of a WTDocument in Windchill and the URL is the details page of the WTDocument.

I have tried to give the label and the URL using the following code, but the value of the attribute is not reflecting:

     WTPartUsageLink usageLink = WTPartUsageLink.newWTPartUsageLink(part, part.getMaster());

     part = (WTPart) WorkInProgressHelper.service.checkout(part, WorkInProgressHelper.service.getCheckoutFolder(), "").getWorkingCopy();

     PersistableAdapter obj = new PersistableAdapter(usageLink, null, Locale.US, new UpdateOperationIdentifier());

     obj.load("LabelControl");

     String url = getDetailsURL(doc); //gets the url of the WTDocument

     Hyperlink link = new Hyperlink(url, label);

     obj.set("LabelControl", link);

     obj.apply();

     PersistenceHelper.manager.modify(usageLink);

     WorkInProgressHelper.service.checkin(part,"success part");

How do I do this?

Thanks in advance.