Can not use PSI for timesheet

[NAMSALR]

Project Server 2007
Can someone provide me a piece of code using PSI who would allow me to:
Add and or Update a timesheet custom field.
adjust timesheet actuals...

I've read the Project Server SDK and I completly lost....

for the time being, I haev tried this for updating the timesheet custom
field :
WSTimeSheet.TimesheetDataSet timesheetDs;
//WSTimeSheet is the timesheet web service...
http://myserver/pwa/_vti_bin/psi/timesheet.asmx
timesheetDs = timeSheetSvc.ReadTimesheet(myTSUid);
WSTimeSheet.TimesheetDataSet.CustomFieldsRow cfr =
(WSTimeSheet.TimesheetDataSet.CustomFieldsRow)timesheetDs.CustomFields.NewRow();
//some code to fill the cfr row
timesheetDs.CustomFields.AddCustomFieldsRow(cfr);
timeSheetSvc.QueueUpdateTimesheet(jobUid, tsGUID, timesheetDs );
the problem occure on QueueUpdateTimesheet with this:
Queue request Failed for Job ID ed059edb-1b99-462a-a930-4dd5d7d4b0a0.
<?xml version="1.0" encoding="utf-16"?>
<errinfo>
<general>
<class name="Queue">
<error id="26000" name="GeneralQueueJobFailed"
uid="a3cf67fa-c9d9-45c3-9c58-1fc2830e2e61"
JobUID="ed059edb-1b99-462a-a930-4dd5d7d4b0a0" ComputerName="MICROSOF-GM3FBO"
GroupType="TimesheetUpdate" MessageType="UpdateTimesheetMessage"
MessageId="1" Stage="" />
</class>
</general>
</errinfo>

in advance many thanks for your help...
ps: sorry for ma writting... english is not my native language....