[displace] formula problem

[rghstocks@xxxxxxx]

I can't seem to figure out how to write an indicator that would show the difference between a displace moving average compared to the same regular moving average similar to below. The [displace] only works for a plot, not for a formula.  Can someone tell me how to write this?
[Displace](AverageFC( Price, Length ) - (AverageFC( Price, Length )
Thanks
Randy