Question in the title.
C# or Vb NET or VBA.
I'm wondering if this needs to be done programmatically or if you're looking for a way to edit tags in bulk. You mention using VBA, which in my experience a lot of the time means using Excel. Would something like the PI Builder add-in for Excel suit your needs or do you need to build out a separate application for editing pointtype?
Not trying to discourage programming, just don't want to have you reinvent the wheel is all. If this needs to be done programmatically, I would recommend checking out the AF SDK's SetAttribute and SaveAttribute methods on the PIPoint Class
Just as a side note, in order for a point type attribute to be changed successfully, you must change between point types that can be coerced. (Allowable point type coercions)
If you want the previously archived data to reflect the new point type, you can reprocess your archives off-line to convert the stored events to the new point type.
Retrieving data ...