I am not sure what you are asking, because if you can “mark a spot” i.e. set a “waypoint,” then you should be able to read the coordinates from that waypoint and use them to post the cache on the caching web site that you are using. On my GPSr (Garmin 60CSx), when the waypoint is set, the coordinates are displayed. One small suggestion: when you are hiding a cache, if your GPSr is capable of doing this, give it several minutes to “average” its reading. If your unit is not capable of averaging, then take several readings over a few minutes and average them yourself prior to posting the cache.
I am not sure what you are asking, because if you can “mark a spot” i.e. set a “waypoint,” then you should be able to read the coordinates from that waypoint and use them to post the cache on the caching web site that you are using. On my GPSr (Garmin 60CSx), when the waypoint is set, the coordinates are displayed. One small suggestion: when you are hiding a cache, if your GPSr is capable of doing this, give it several minutes to “average” its reading. If your unit is not capable of averaging, then take several readings over a few minutes and average them yourself prior to posting the cache.