I have tried a tide of times, I would want to create a pointer where there is the price is moved behind of 50 periods and add last closing is equal for last the 50 periods:
to: =ref (c, 50);
b: =ref (lastvalue (c), - 50);
a+b
so that in the lacking space there is from adding the same last chisura for the 50 periods, I do not succeed to add together there is t someone to help me?

I have tried also with the formulas isdefined I succeed to only create two pointers but not one