The following should work:
1) click on the "Target files" button in the project window.
2) right-click on yourname.lib and select "Properties" from the context menu. For a Win32 Lib project, you should see the following command: $(AR) $(ARFLAGS) -out:"$@" $**.
3) add the extra library after this command - something like this: $(AR) $(ARFLAGS) -out:"$@" $** extra.lib
4) build your project.
Pelle