Who can help me design a fixture family as follows:

I need to follow a winding cove with LEDs that populate at 4" increments. This has to be flexible like a CAD spline and populate the LEDS as necessary. As it is I am placing these 4" fixtures around 1000s' of feet of cove that periodically changes and the task is tedious and annoying. Also, I have some fixtures that are straight but different lengths. I can modify length but is there a way to add electrical data based on linear feet of fixture. For example, a 3' fixture that is 2.5VA per linear foot would be 7.5VA. With an instance parameter that changes length many times can I calculate the VA with Revit and have that data be available to my electrical systems in MEP without manually entering it. I have tried defining the fixture length in number (2 instead of 2' 0" or 1.5 instead of 1' 6") format then using it in a formula for VA but the error warns incompatable formula because VA is electrical and number parameters cannot coincide. Any help is great, thanks.