Not out of the box, though if Project Server provides an SDK where you can programmatically query for data, you could write a UDF to get the data through the SDK, and return it to the workbook loaded in Excel Services.

I don't know much about Project Server, but you can check out this post on how to use the SharePoint SDK to get SharePoint List data into the workbook on Excel Services, and you could do the same with the Project SDK assuming there is one: http://blogs.msdn.com/luisbeonservices/archive/2006/09/28/consuming-sharepoint-lists-in-excel-services.aspx

- Luis

Did the answer above work out for you

If not please let us know so we can try and continue helping, otherwise, please mark it as the answer for the thread so we can get it off the radar.

Thanks!

Possibly, I'm not sure, you might have to ask around on a BDC forum (I'm not much of a BDC expert).

If that's the case than you could use a UDF to get the BDC data into Excel Services and indirectly getting your Project Server data.

- Luis