accessing m-files located in different paths

let's say i have
C:\scripts\first\myfile.m
C:\scripts\myfile2.m
C:\scripts\myfile3.m
C:\scripts\myfile4.m

myfile.m:
  [A,B] = myFile2(signal);

myfile2.m:
function myFile2(signal)
  [Aw,Bw] = myfile3(signal)


you get the idea...
C:\scripts\first\myfile.m starts the chain reaction and the scripts in C:\scripts then call each other

How would you set this up in C:\scripts\first\myfile.m ? (with relative paths)