Adodb Command.Execute() - type value error

I was experimenting with ADO and the "CREATE PROC" SQL to create stored procedures in an Access 2002 database.  I started with an example that used Northwind.

I then wrote a short VBS function to execute the Procedure via the adodb.command object -  I first tried it by using CreateParameter() and Append, but kept getting a type value error when executing - however, if I pass the parameters to the function then include them as an optional array (the 2nd parm of cmd.Execute() ) it works fine.  Most of the examples I have seen don't use the 2nd parameter, so I was wondering, is there a bug in Jet 4.0?  -  

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function runcmd(nRec,cName)
' this is the query in Access
'PARAMETERS inProductID Long, inProductName Text ( 40 );
'UPDATE Products SET Products.ProductName = inProductName
'WHERE (((Products.ProductID)=[inProductID]));


Set conn = CreateObject("adodb.Connection")
conn.Open("PROVIDER=Microsoft.Jet.OLEDB.4.0; Data Source=C:\Program Files\Microsoft Office\Office10\Samples\northwind.mdb;")
Set cmd = CreateObject("adodb.Command")
cmd.ActiveConnection = conn
cmd.CommandText = "procProductsUpdateItem"
cmd.CommandType = 4

' if the next 3 lines are executed you get a "Type Value" error
cmd.Parameters.Append cmd.CreateParameter("inProductID",139,1,,2)
cmd.Parameters.Append cmd.CreateParameter("inProductName",129,1,40,"New Chang")
cmd.Execute , , adExecuteNoRecords

' however, if you pass the function parameters to an array, it works fine
'cmd.Execute ,Array(nRec,cName), adExecuteNoRecords
Set cmd.ActiveConnection = Nothing
Set cmd = Nothing
conn.close
Set conn = Nothing
runcmd = 0
end function

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stan