HistoryID Problem?

Hi I'm trying to use SOAP in a VAB Access 2003 Project. I can connect to the Reporting Services an Create fr example Folders. But if I want to Render a Report i am Getting a Problem.
Error: -2147221504
For ' snapshotID ' indicated parameter value does not correspond to the type of parameter.
I passed an empty String for the optional Value HistoryID.
I dont know where the problem is.
Can anybody help me ?
CODE:
Dim ReportName As String
Dim RenderFormat As String
Dim HistoryID As Variant
Dim DeviceInfo As String
Dim Parameters(2) As struct_ParameterValue
Dim Credentials() As struct_DataSourceCredential
Dim ShowHideToggle As String
Dim resultFile() As Byte
Dim resultEncoding As String
Dim resultMimeType As String
Dim resultParametersUsed() As struct_ParameterValue
Dim resultWarnings() As struct_Warning
Dim resultStreamIds() As String
Set RS = New clsws_ReportingService
ReportName = "/SampleReports/Employee Sales Summary"
RenderFormat = "mhmtl"
HistoryID = 0
DeviceInfo = "<DeviceInfo><Toolbar>False</Toolbar></DeviceInfo>"
ShowHideToggle = ""
Set Parameters(0) = New struct_ParameterValue
Parameters(0).Name = "EmpID"
Parameters(0).Value = "38"
Set Parameters(1) = New struct_ParameterValue
Parameters(1).Name = "ReportMonth"
Parameters(1).Value = "6" ' June
Set Parameters(2) = New struct_ParameterValue
Parameters(2).Name = "ReportYear"
Parameters(2).Value = "2004"
resultFile = RS.wsm_Render( _
ReportName, _
RenderFormat, _
nil, _
DeviceInfo, _
Parameters, _
Credentials, _
ShowHideToggle, _
resultEncoding, _
resultMimeType, _
resultParametersUsed, _
resultWarnings, _
resultStreamIds)
thx for your helpSorry for double posting... but there was an error maeesage so i tryed again.sql