|Determine the "identity" of your emails. Set with SAM the sender and the folder folder for sent items with the help of rules.
This example moves the due date of all selected task items by four weeks. More precisely, we move by 4*7=28 days in order to preserve the original weekday.
Public Sub MoveTaskDueDates()
Dim Exp As Outlook.Explorer
Dim Sel As Outlook.Selection
Dim Task As Outlook.TaskItem
Set Exp = Application.ActiveExplorer
Set Sel = Exp.Selection
If Sel.Count Then
For Each Task In Sel
Task.DueDate = DateAdd("d", 28, Task.DueDate)