Problems whit the function Count.If for correlatives

Hi, i have a problem whit this function..... i have a table and in the first column i want a correlative that count the number of times that a cod_id exist in another column but in the specific row that im working.... so i used this function:

but when i add another cod_id and the table create the new row the funcion have a automatic change.

the c10 must to be c9 but it changed automaticly.... please Help!!!!!