As indicated you cannot use a dynamic number in the namemap. You could use it in code and make a call to FindElement. However, it appears as if the data you are looking for is in a table that can change. Additionally any xpath with something such as //td/th[64] means that it is looking for the 64th instance of that object within the HTML. In my opinion, this xpath is very susceptible to changes (especially if it is in a table). I would not map objects in a table, but rather write code that can be used to find the items that you are looking for.
