In After effects how can I store the start and end point values of a gradient on one layer to generate the opposite values in another layer my composition width is 4480
I have 2 layers with a gradient ramp on each
once I've entered the start and end position of the gradient on the first layer I need to have the opposite equivalent start and end position values of that gradient generated in the second layer's gradient.
So with a comp width of 4480 if gradient 1 start x is 1000 and end x is 1250 then gradient 2 start x should be 3480 and end x is 3230. The Y is going to have a fixed position.
Ideally I'd like to tie in the start x and end x of the first graident to an expression control such as a slider so i can  adjust the position of the points simultaneously.
This is very similar to your other question:
In After Effects how can I generate the value of an opposite x position and then send that value to an effect on another layer?
The answer is the same. Use a pick whip to link two controllers together.