Not able get value using RequestState

Hi, I have created one method called set_project_name in VB and run this method on OnAfterLock of "GRIL Project" ItemType

Dim inno as Innovator = Me.getInnovator()

Dim projectID as String = Me.getID()

Dim AML_to_getProjectName as String = "<AML>"+
 "<Item type='GRIL Project' action='get' select='_project_name'>" +
 "<id>"+projectID+"</id>" +
 "</Item>" +
 "</AML>"


Dim ResultProjectName as Item = inno.applyAML(AML_to_getProjectName)
Dim projectname as String = ResultProjectName.getItemsByXPath("//Result/Item[@type='GRIL Project']").getProperty("_project_name").ToString()
 RequestState.Add("projectname", projectname)

Return Me

and I want that value on other ItemType called Document on the event called "OnAfterAdd" like this:

Dim inno as Innovator = Me.getInnovator()

Dim projName As String

projName = DirectCast(RequestState("projectname"), String)

Return Me

  But I got the Null Object. Whether It is possible to get RequestState value on another ItemType?   Thanks in Advance. Regards, Maddy.