A search in the archives will find a number of threads which discuss trimsheet design. One example is
this one in which we discuss the basics of trimsheet workup design. May provide another slant in addition to the Airbus document .. however the basics are pretty standard so the two will cover much the same stuff.
Best option is to scan and post a copy of the particular trimsheet in question and we can pull it apart to show how it has been designed and drawn up (otherwise called "reverse engineering").