is there any way to define sky movement speed in Lite-C?

i do it this way

ENTITY* bla =
{
flags2 = SKY;
}

void sky_speed_startup()
{
while(1)
{
bla.u+=10*time_step;
wait(1);
}
}

is there a more convenient way to do that? uv shifting is too fast for a sky, and lower values(below 0.001) don't move it at all