I've had this problem, and depending on your philosophy, there is either an easy solution or no easy solution. The easy solution is to convert filePreCalc.nb to a package (.m) and load it with Get ("<<filePreCalc.m"). I think if you make all the cells in filePreCalc.nb initialization cells, Mathematica can automatically generate a package for you.
The not so easy solution is to program filePreCalc.nb to call furtherCalc.nb at the end.
(I think the problem arises as follows. The cells to be evaluated are put in a queue. From a single notebook, the cells are evaluated in the order submitted. When there is more than one notebook, the kernel may alternate between the notebooks in selecting the next cell to evaluate. Mathematica does not seem to provide a way to control this.)