the sollution so far I found is to use a generic model ( let's say a cube with as many vertexes we may need to compose the new model) and than using functions
ent_getvertex, ent_setvertex to modify each vertex coordinates.

bellow only y variable is modified.

///////////////////////////////
int i = ent_status(terrain,0); // number of vertices
for (; i>0; i--) {

CONTACT* c = ent_getvertex(terrain,NULL,i);
c.y += 50.0;
ent_setvertex(terrain,c,i);
}