THANK YOU SO MUCH!!! Now it is working perfectly!! :-D
I made exactly what you said and a little more:
A) Column C: =FECHA($E$7,COINCIDIR($D$7,meses,0),FILA()-9)
B) Column J: =SI(C10<=FIN.MES($C$10,1-1),DIASEM(C10,11),8)
I really love this forum!!!
Regards!! :-)