set line item 'rate' from OnPostSourcing event

I'm having a very hard time getting the following code to work:

 function OnPostSourcing(type, fldname)  {   if(type == 'item')   {    alert('OnPostSourcing::fldname: ' + fldname);    nlapiSetCurrentLineItemValue('item', 'price_display', 'custom');    nlapiSetCurrentLineItemValue('item', 'rate', '111.11');   }  } 

When I choose an item from the list, the above event fires.  Here is what is happening (as best I can tell):
[LIST=1]
[*]alert displayed with: 'OnPostSourcing::fldname: price' - the alert stops js processing so I can see the values that were sourced and inserted into the current line, the 'Price Level' is 'Base Price' and the 'Rate' is '37.50' (or default price for the item)