"Aras.Server.Core.ItemNotFoundException" When transitioning from "In Work" to "Preliminary" with ECO Express's WF Activity

Hi Community
I'm having an issue and I'm hoping the community can help me solve it!
In normal ECO Express WF of the Creator's operation goes to " Start--> Preliminary --> In Work" ,but what I'm trying to do is " In Work --> Preliminary"
In other words, moving the workflow back one step.
Therefore I'm using the following peice of code for dynamic voting of workflow :  Dim sbVoteXml As New Text.StringBuilder("")
            sbVoteXml.Append("<Item type=""Activity"" action=""EvaluateActivity"">")
            sbVoteXml.Append(" <Activity>{0}</Activity>")
            sbVoteXml.Append(" <ActivityAssignment>{1}</ActivityAssignment>")
            sbVoteXml.Append(" <Paths>")
            sbVoteXml.Append(" <Path id=""{2}"">{3}</Path>")
            sbVoteXml.Append(" </Paths>")
            sbVoteXml.Append(" <DelegateTo>0</DelegateTo>")
            sbVoteXml.Append(" <Tasks />")
            sbVoteXml.Append(" <Variables />")
            sbVoteXml.Append(" <Authentication mode="" \ "" />")
            sbVoteXml.Append(" <Comments></Comments>")
            sbVoteXml.Append(" <Complete>1</Complete>")
            sbVoteXml.Append("</Item>")            Dim itmVote As Item = Inn.newItem()            itmVote.loadAML(String.Format(sbVoteXml.ToString(), sActivityID, sAssignID, sPathID, In_REVIEW))
            itmVote = itmVote.apply()However, I got the error "Aras.Server.Core.ItemNotFoundException"...The "Preliminary" activity state is "closed", which may be the cause, but I don't know how to solve it.
Do you know how to move the activity back one by using a server method etc.?
In addition, should I think about "PE_ChangeItemTransition" too?(This Aras's standard method perform validation of Change item(ECN, ECO, etc..) which situated in state or promoted to another state)Could someone please let me know why this error is happening.
I will be happy to help you with other information as needed.
Thank you.