How about a spiral effect, pick white as the color (for subsequent masking), pick the number of spirals and their width, and set the movement to zero so it just stays fixed, THEN do a morph UP in a second layer and then figure out the layer 1 is mask/unmask etc. I forget exactly how those masks work but I am thinking that if the spiral is white and you set it as the mask, then the morph on a later below going up should only show the color where there is white and the spiral should fill.
Louie