nel file js esterno prova a mettere:


document.write("<scr"+"ipt src='script1.js' type='text/javascript'></scr"+"ipt>");
document.write("<scr"+"ipt src='script2.js' type='text/javascript'></scr"+"ipt>");
document.write("<scr"+"ipt src='script3.js' type='text/javascript'></scr"+"ipt>");