InfoPath Dev

I'm trying to add some sample code to a button, for a browser form in SharePoint Online 2013. I understand that browser forms and SharePoint online 2013 are both able to deal with code behind When I want to edit the code in Visual Studio 2012, I get errors because of missing SharePoint namespace in the Microsoft namespace. I found lots of post about changing the .NET framework, or the target platform to solve this. None of them made any difference. Now I'm starting to think that I may require a local Microsoft.SharePoint.dll, even though I work in the cloud. Can someone confirm this? Thanks

 The SharePoint DLL should only be needed if your code makes use of the SharePoint object model. So in short, it should be entirely possible to write InfoPath code behind for a lot of tasks without this DLL.

Thank you Jimmy. In this case my code (based on somebody else's sample code) did make use of the SharePoint object model so the ddl was required. I did manage to find it, but then ran into permission issues because my form now needs to be sandboxed (I mentioned this in another post which was also kindly ansewered by you).

Thanks.