Hi,
Use iTween or another tweening engine for this.
OR, interpolate taking in account the delta time ( that you can get using the "gettimeinfo" action).
you are having jerky results likely because of framerates fluctuation, the key is to animate NOT frame dependant but time depending, so with itween, you specific a time and/or if you want to manbually do it, include the deltatime into your math to remove any frame rate dependancy.
bye,
Jean