RTNav Not getting set?

We are trying to navigate through the rich text to find some strings, but I am not getting the variable set for rtNav. When I look at the variables in the debugger, the rtRange is set and has properties, but the rtNav does not.

Set rtNav = rtitemTo.CreateNavigator

Set rtRange = rtitemTo.CreateRange

If rtNav.FindFirstString(searchstr) Then

Call rtRange.SetBegin(rtNav)

Call rtitemTo.BeginInsert(rtRange)

'this may not work to insert rtitem from other document but we can use text just as well.

Set rtitemFrom = doc2.GetFirstItem(“Body”)

Call rtitemTo.AppendRTItem( rtitemFrom )

Call rtitemTo.AddNewLine(1)

Call rtitemTo.EndInsert

Call rtRange.FindandReplace(searchstr, " ")

End If