open acad drawings within excel VBA

[kato01]

The following code works to check if autocad is already running

Dim AcadApp as AcadApplication
If AcadApp Is Nothing Then
        Set AcadApp = CreateObject("AutoCAD.Application")
Else
        Set AcadApp = GetObject(, "AutoCAD.Application")
End If

great thanks to Tommy

I just tried this on VBA of EXCEL 2010. It simply does not work. I get the following error message:
user-defined type not defined
when I debug, the error refers to the line below

Dim AcadApp As AcadApplication

Am I missing something?

Thanks