ALL excepect function with if condition

Greeting members , 

i want to create a calculated column using IF and all expect if possible . 

here is a sample of data  : 

i want to create the G.Note column , this column will have the NULL(or the value from another column) value if the same ID got the same note (as you can see the ID=2) 

i think im able to acheive this using allexpect but im missing the right sentence .

Thanks all in advance .