by ent_getvertex it is possible to access the D3DVERTEX pointer of any model/terrain vertex called c.v if:

CONTACT* c = ent_getvertex(entity,NULL,vertex_number);

and as described in atypes.h:

typedef struct {
float x,y,z; // position in DirectX coordinates
float nx,ny,nz; // normal
float u1,v1; // first coordinate set, for textures
float u2,v2; // second coordinate set, for shadow maps
float x3,y3,z3,w3; // third coordinate set, for tangent vector and handedness
#ifdef A8
float tu4,tv4; // 4th coordinate set, for additional data
#endif
} D3DVERTEX;

very similar to mesh deformation, but now c.v.u1 and v1 are what you need (floats!). And then ent_setvertex(entity,c,vertex_number);