Form scripting...

I am looking to do my first bit of form scripting, I need to update the name field on the project relationship form to be the Opportunity + " - " + Account

Now I have gone into form properties and tried to modify an example helloWorld function - 

Function helloWorld()
{
    var varMyAccountValue = Xrm.Page.getAttribute(“Account”).getValue() ;
    var varMyOpportunityValue = Xrm.Page.getAttribute(“Opportunity”).getValue() ;
    var varMyOpportunityAccountValue = varMyOpportunityValue + " - " + varMyAccountValue

   alert("Details " + varMyOpportunityAccountValue );
}

Then in the Field Properties for Account I have added the helloWorld.

Now if I try to preview it doesn't appear to have worked as nothing happens but when I close the form, I receive an error message:

CrmScriptErrorReport>
  <ReportVersion>1.0</ReportVersion>
  <ScriptErrorDetails>
   <Message>The value of the property 'helloWorld' is null or undefined, not a Function object</Message>
   <Line>298</Line>

Can anyone point me in the direction of where I am going wrong?

Matt