Installing New Print Processor in Win2k

I need to install a new print processor in Windows 2000 Pro. I found the following API call that is supposed to do it, but can't get it to work:

Private Declare Function AddPrintProcessor Lib "winspool.drv" Alias "AddPrintProcessorA" (ByVal pName As String, ByVal pEnvironment As String, ByVal pPathName As String, ByVal pPrintProcessorName As String) As Long

...
If AddPrintProcessor(vbNullString, vbNullString, "C:\NewPrintProc\PrintProc.dll", "NewPrintProcessor") Then
MsgBox "Successful installation.", vbOKOnly, "Success"
Else
MsgBox "Error: " & GetLastError, vbOKOnly + vbCritical, "Error"
End If
...

Does anyone know what I am doing wrong? Is this the best method to add a new print processor?

Steve