maximum count arguments

[Jeroendedekker]

I need to set in a maximum count of arguments in my excel sheet 

eg: when there are already 3 arguments in a row that you can't set a 4th argument in this row.

[#2]

@Jeroendedekker 

you can use data validation 

for example select the 1st row, then go to data validation, select custom

and write

=counta(1:1)<=3

then save.. this way it will only allow three cells to be modified, otherwise it will not accept the input