First question is are you using a weather station like a kestrel
? If not then you will have to get the altitude from your gps to punch it in to shooter and get the baro, temp and other stuff from a local weather station on the Internet.
If you are using a kestrel then you can set your kestrel altitude to 0 and get the station pressure from your kestrel and put that in shooter for your baro pressure. If you are doing it this way then you will need to go into shooter under the atmosphere section and turn "pressure is absolute" to ON. If you do it this way with a kestrel, you will never have to worry about what altitude you are at.
Either way you do it..your dialing should not be off at all no matter what elevation you are at.