This code will take you most of the way, you just have to pass a valid
MAPIFolder reference to the procedure and desing a custom message box form
that will be big enough to display the message body text:

Sub SearchForRejectedReports(SourceFolder As Outlook.MAPIFolder)
'The SourceFolder argument requires that a reference to the folder that is
to be searched
'be passed to this procedure
'Use either NameSpace.GetDefaultFolder, or walk the Folders collection of
any folder to get the desired
'MAPIFolder object reference

   Dim objItems As Outlook.Items, objMsg As Outlook.MailItem
   Dim intX As Integer
   
   Set objItems = SourceFolder.Items
   objItems.Sort "Received", True
   For intX = 1 To objItems.Count
       If objItems.Item(intX).Class = olMail Then
           'Found the most recent e-mail message
           Set objMsg = objItems.Item(intX)
           If InStr(1, objMsg.Body, "rejected", vbTextCompare) > 0 Then
               'This message contains the word "rejected"
               'You'll need to design a custom form to mimic a message box
that would be
               'big enough to contain the text of the message body which is
available here
               'by calling the value of objMsg.Body
               GoTo Leave:
           End If
       End If
   Next
   
Leave:
   Set objItems = Nothing
   Set objMsg = Nothing
End Sub