こういう感じのとは違うん？

Private Sub Command1_Click()
Dim fso As Object
Dim objname$, pth$
objname = "Scripting.FileSystemObject"
Set fso = CreateObject(objname)
pth = CallByName(fso, "BuildPath", VbMethod, "c:\windows", "test.ini")
Debug.Print pth
End Sub