Not sure what the main question is as I am still confused about the "copy to another sheet"!?
As I see that the Odesolve throws an error, maybe doing as follows will do the job - I didn't wait for ODEsolve to finish, though.
Notice that instead of Ec1 OF second derivative we have now Ec1 of 1 TIMES the second derivative, etc.
Looks like Mathcad doesn't like the second derivatives to be arguments of functions. Could be thats because the function is defined by a symbolic evaluation but I guess Mathcad doesn't like any function there.
Just tried it - you cannot put the derivative as argument of any function here.
Of course the workarund given will only work for that specific kind of function Ec with the result that Ec1,2,3(x) is just a multiple of x.