Catch Points: Battering upwards from above

Catch Points: Battering upwards from above ground string to meet Natural

Need to be able to batter upwards from my string to meet the surrounding natural surface. If my origin string is above natural surface i cannot produce a batter that rises away from the string to meet natural using "catch points". It is possible in roads module by entering a negative fill batter value into the "side slopes" function. Magnet has the ability to do this, it's just not available as part of "catch points".