Flight performance means different weights, altitudes and some other parameters. Excel is limited to 2D-matrices.
For example: I want to calculate Rate of Climb for a given weight over the entire Mach/Speed-Altitude region.
First I need local speed of sound and air density for each altitude-Mach pair.
Then the lift coefficient.
Then using an analytical drag model the drag (if I have a look-up table or a hybrid with analytical polar but look-up zero lift drag it gets tricky).
Thrust is usually a look-up table, so again a big pain when using Excel.
The resulting calculations from this point on are rather simple.
One can use Excel with some Visual Basic scripts, but then a real programming language might quickly become more handy. I am using Matlab, a similar but free software is Scilab. Easy to program, easier than Excel
VB.