Cannot access the return value of a PostgreSQL function using ADO

Hi,
I have a Postgres function

CREATE OR REPLACE FUNCTION updateconfigitem(inputkey character varying,
inputvalue character varying,
modifier character varying)
RETURNS integer AS
$BODY$
BEGIN
UPDATE configitems
SET _value = inputvalue,
_modifier = modifier
WHERE _key = inputkey;
RETURN 1;
EXCEPTION
WHEN others THEN
RETURN 33;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;

I call it from a VB6 program using ADO

Dim objCmd As ADODB.Command
Dim colParams As ADODB.Parameters
Dim objParam As ADODB.Parameter
Dim lngRETURN_VALUE As Long
Dim strSQL As String

' Set connection properties and open
Set objCon = New ADODB.Connection
objCon.ConnectionString = "DATABASE=MYdatabase;UID=MyUser;PWD=Mypassword;DSN=PostgreSQL30"
objCon.CursorLocation = adUseClient
objCon.Open

Set objCmd = New ADODB.Command
' Set command properties
With objCmd
Set .ActiveConnection = objCon
.CommandTimeout = m_lngCommandTimeout
.CommandText = "updateconfigitem"
.CommandType = adCmdStoredProc
Set colParams = .Parameters
End With

' Define stored procedure params and append to command.
colParams.Append objCmd.CreateParameter("RetVal", adInteger, adParamReturnValue, 0)
colParams.Append objCmd.CreateParameter("inputkey", adVarChar, adParamInput, 50)
colParams.Append objCmd.CreateParameter("inputvalue", adVarChar, adParamInput, 255)
colParams.Append objCmd.CreateParameter("modifier", adVarChar, adParamInput, 255)

' Specify input parameter values
colParams("inputkey") = "colour"
colParams("inputvalue") = "Green"
colParams("modifier") = "mg"

' Execute the stored procedure
objCmd.Execute

End Sub

When I execute I get error
"Run-time error '-2147467259(80004005)': ERROR: could not determine data type of parameter $4; Error while executing the query"

If I remove the line creating the return parameter

colParams.Append objCmd.CreateParameter("RetVal", adInteger, adParamReturnValue, 0)

the program works OK. I use the same type of ADO definition to call MS SQLServer stored procedures and I can pick up the return value.

What do I need to do to get the Postgres Function Return Value?

I am developing on a Windows 7 Professional (SP1) operating system. Using Microsoft Visual Basic 6.0(SP6), Microsoft ActiveX Data Objects 2.7 Library and PostgreSQL version: 9.5.4

Regards,

Mick Griffin
Software Engineer
BTS Holdings PLC

DDI: +44 (0)20 8401 9003 Fax: +44 (0)20 8401 9101
http://www.bts.co.uk

BTS Holdings PLC - Registered office: BTS House, Manor Road, Wallington, SM6 0DD - Registered in England: 1517630

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