Infopath Code behind

Hi,

I have a infopath 2010 form with multiple views. I want to update form library (which current form is published) field value when a button is clicked in the form. When i opened code editor its is opening in visual studio 2005 and not able to add Microsoft.sharepoint.dll reference because the target framework is 2.0. How can i use visual studio 2008 or 2010 for infopath code behind? or else how can i get reference to Microsoft.sharepoint.dll in visual studio 2005, so that i can call form library using object model.

Any help appreciated....