Is it possible to write 261 to the interface string which is already interfaced to ground model

Hi,

Could any one can help on this.

I want to create interface as in below image. If it is cut its a different section which I have no problem. When it comes to fill location, couldn't able to create a flat string from the 1in3 slop string which is interfaced to ground model from there for offset of 15m flat following berm as shown in image.

INTERFAC,RAIL GMC NEW TRIA,RAIL GMC NEW
259,INTI
260,M000,2=IA00,3=IB00,4=-1,5=35000,8=53500


000 FILL
262,TX00,2=C000,3=IB01,4=5,7=-0.33333333
262,IGN ,2=IB01,3=IB02,4=3,5=15.0,7=0
262,IGN ,2=IB02,3=IB03,4=5,5=04.0,7=0.5
262,IGN ,2=IB03,3=IB04,4=3,5=01.0,7=0
262,TX00,2=IB04,4=5,7=-0.5


000 CUT
261,IGN ,2=C000,3=IA01,4=5,5=3.6,7=-0.33333333
261,IGN ,2=IA01,3=IA02,4=3,5=6.0,7=0
261,IGN ,2=IA02,3=IA03,4=5,5=3.0,7=-0.33333333
261,IGN ,2=IA03,3=IA04,4=3,5=5.0,7=0
261,IGN ,2=IA04,3=IA05,4=5,5=3.0,7=+0.33333333
261,TX00,2=IA05,4=5,7=0.25
263,DISC
999

Many thanks in advance.