relay help for my light bar on my truck can anyone help

well I have a semi truck and a light bar with 12 marker lights in the
bumper I am going to wire them 6 and 6 so when I turn on the turn
signal they flash the right way 6 will flash right and 6 will flash
left I would like to go further and make them flash in a seires
1,2,3,4,5,6, how do I do this. what relays do i need and or anything
eles I would like them to start to flash in the center at number 6 and
flash one at a time down to 1 and work there way to the out side of
the bar so it would be 1,2,3,4,5,6 6,5,4,3,2,1,and start over again.

left side right side