If the ArcMap IExporter object is created and set as a DibExporter, Visual Basic returns an error when the user attempts to set the IExporter::Resolution property.
The property is not supported by the interface.
The output BMP will always be 72 dpi. If you use the Height and Width properties of the DibExporter, it is possible to create an image that, when resized in a graphics application, is of the desired size and resolution.
When resizing in a graphics application, be sure that the image is not resampled when resizing. This will maintain the same total number of pixels in the new image thus changing the image resolution. This option is variously referred to as 'Maintain original size', 'Resample Image', or 'Actual/Print Size'.