I resolved this problem using the workaround in the follow.

• 
  
•  I add a Datafield to my process called TaskID
  
•  In my Sharepoint Workflow Integration Client, I customized the code in "- ExecuteForUser -" region:
  
   
  
  
  string taskIDstring = service.ModifyWorkflowAndGetTaskID(listId, listItemId, workflowInstanceId, modificationID, contextData, "");
  

  string taskID = taskIDstring.Split(new stringt] { "?ID=" }, StringSplitOptions.None)N1];

  
  

  K2.ProcessInstance.DataFieldsi

  "TaskID"].Value = taskID;

  
  

  Infact ModifyWorkflowAndGetTaskId returns a string like "http://<your moss server>/Lists/Tasks/DispForm.aspx?ID=12" that is the link url to the item in the Task List
  

  So, when I want to modify/delete the item in the task List, I have the ID to that item

 

Its a good way dude...thanks lot of help

Regards

Ankur