CS-RCS commands always work with the "current" branch (see previous FAQ). You should either select the branch from the GUI or from command-line (e.g. VB script) using the COM API. For example:
Sub Macro4()
Dim rcsapp As Object
Set rcsapp = CreateObject("Csrcssrv.Application")
Dim st As Boolean
st = rcsapp.SetBranch("MyProject", "branch1")
Set rcsapp = Nothing
End Sub
You should call rcsapp.SetBranch("MyProject", "<Trunk>") to switch back to the main trunk.