Well, in that case:
Code:
new Float: fvAngle[3];
pev(id, pev_v_angle, fvAngle); // Get player's view angle
angle_vector(fvAngle, ANGLEVECTOR_FORWARD, fvAngle); // Transfer angle vector to a vector
xs_vec_normalize(fvAngle, fvAngle); // Create unit vector
xs_vec_mul_scalar(fvAngle, 200.0, fvAngle); // Multiply vector by 200.0
After that, fvAngle[] would be velocity you want to set for your grenade. Red number in code above is velocity you want to set.