I write custom functions that work well; I write macros that work well too; but when both are installed in the same VBA project(in separated modules), the execution becomes erratic: for ex. the focus jumps from one line in the middle of macro#1 to another line in a custom function......
What is wrong ? Should I provide a copy of the code, or is the problem at another level?

A macro is a public subroutine that doesn't have any parameters. You can't have a macro and a subroutine that have the same names in the same project.

(The macros and functions have all different names).
I found that every personal function (using "Application.Volatile") present in some cell's formula is automacally recomputed after each change made by a macro in any cell.
So I solved my problem using the following code at the beginning of evry macro: Application.Calculation = xlCalculationManual
And at the end: Application.Calculation = xlCalculationAutomatic

Is that THE solution, or does a better practice exist?