##KOMKE I think the custom battlefields are "scn_1257_combat_swamp_0", "scn_1257_combat_rocky_desert_0" because the variable $tom_use_battlefields is the one checked in the menu option "use custom battlefields"
        (try_begin),
          (assign, "$tom_generate_swamp", 0),
          (assign, "$tom_generate_desert", 0),
          (assign, "$tom_generate_desertv2", 0),
          (assign, "$tom_generate_desertv3", 0),
          (assign, "$tom_generate_iberian", 0),
          (assign, "$tom_generate_iberian2", 0),
          (assign, "$tom_generate_snow", 0),
          #(assign, "$tom_generate_euro_forest", 0),
          (eq, "$tom_use_battlefields", 1),
          (try_begin), #extra check for custom field
            (eq, ":terrain_type", rt_forest),
            (store_random_in_range, ":random", 0, 101),
            (ge, ":random", 60),
            (store_random_in_range, ":scene_to_use", "scn_1257_combat_swamp_0", "scn_1257_combat_rocky_desert_0"),
            (assign, "$tom_generate_swamp", 1),
            #resourcehungry forests
            # (else_try),
            # (eq, ":terrain_type", rt_forest),
            # (lt, ":random", 40),
            # (assign, ":scene_to_use", "scn_1257_combat_forest_0"),
            # (store_random_in_range, ":random", 1, 3),
            # (assign, "$tom_generate_euro_forest", ":random"),
          (try_end),