Set Web resource fields value to MS CRM 2013 Entity

Hi Team,
In the CRM entity we have one button. When we clicked on that button one HTML popup page will be opened.
In the HTML page we have one Text box. I need set this text box value into CRM entity text box.
I am using below code:
window.parent.Xrm.Page.getAttribute('mscrmfieldname').setValue(value);
but this code not working.
I am using MS CRM 2013 version.
Please help me.