Disable 'New' and 'property' button on 'Look up record' form on CRM 2011

Hi,

I have a custom view with disabled view picker but on that lookup record form I have to disable 'New' and 'property' Button . I have tried with below codes but it is not working :-

var lookupcontrol = Sys.Application.findComponent("attributename");

if(lookupcontrol ! = null){

lookupControl._element._behaviors[0].AddParam(“ShowNewButton”, 0);

 }

or

LookupAddress.AddParam("parentType", window.dialogArguments.Xrm.Page.data.entity.attributes.get("attributename").getValue()[0].type);

Please suggest for the same .

Thanks in Advance