wscript exec cmd.exe /c does not report error - windows

Question

I try several version of Wscript exec method.
If i use a cmd.exe /C MyRequest, the execution does not report an error if the MyRequest is failing but return the error if cmd.exe /c is not used.
I was thinking that cmd.exe is reporting the return code of the call to the MPyRequest but seems not. How to retreive the return code in this case.
Here is the simplified version of my test (comment direct version to have the non failure)
Environnement will be mainly windows 7 (normaly no other system, maybe XP)
' Missing.cmd does not exist to force the failure test
'version with cmd.exe (CmdDir content is a valid and working cmd.exe)
ExecCmd = CmdDir & " /c Missing.cmd 1"
' direct version
ExecCmd = "Missing.cmd 1"
Set objShell = CreateObject("WScript.Shell")
On Error Resume Next
Set oExec = objShell.exec( ExecCmd)
' -- Post treatment ---------------------------
If ( err.Number = 0) Then
If ( oExec.ExitCode = 0 ) Then
' No error
wscript.echo "Execution OK"
Else ' Exit with error
wscript.echo "Error :" & oExec.ExitCode
end if
Else ' error on exec itself
wscript.echo "Execution. Error on object at call: " & err.Number _
& " Source: " & Err.Source & " Desc: " & Err.Description
end if
Solution based on all your reply (thanks all) [ #Damien, #Ekkehard.Horner, #Hans Passant]
check error (via on error and err.Number) for vbs internal error like bad variable/method call. This should be at exec call sub level (so not at main process if exec call is in a function/subroutine)
exec.status to wait until it change to 1. Wait is a following process checking the status, not like a shell.sleep
during this wait, catch stdout/stderr with a AtEndOfStream if life info is needed (if not, read after the close of the process)
for a timeout process, use a cycle of shell.sleep with an exit (of cycle) if timeout or other event is trapped (I use a counter associate to a clock time/sleep time in this case) and exit the loop if trigger occur associate with a exec.Terminate to kill the process in this case (depending of your need ...)

Answer 1

You need to check the ExitCode property.

Answer 2

If it is actually returning an error code, perhaps you are processing exitcode to early. Maybe add in oexec.StdOut.ReadAll() to make it wait until completion.
Perhaps you could add in something like this
....
....
Set oExec = objShell.exec(ExecCmd)
oExecResult = oexec.StdOut.ReadAll()
SessionExitCode = oexec.ExitCode
' -- Post treatment ---------------------------
If ( err.Number = 0) Then
If ( SessionExitCode = 0 ) Then
' No error
wscript.echo "Execution OK"
Else ' Exit with error
wscript.echo "Error :" & SessionExitCode
end if
Else ' error on exec itself
....
....