Excel formula, If/and/or

It is not clear what you exactly want, as there is a whole cross product of possibilities:

C6 could be <8, or <=16 or (between 16 and 17 or) >17, and

C7 could be <6, or <=12 or (between 12 and 13 or) >13.

Each of the four options of for C6 can be combined with each of the four options of C7, resulting in 16 possibilities; your formule seem to only look at three or six.

Anyway, I'll take a guess and let you adjust it if this is not what you wanted. Let's develop it step by step:

A. if either one is above the upper limit, you want it to fail:

=IF(OR(C6>17,C7>13),"! Check With TD !","later")

B. then we add the result '2':

=IF(OR(C6>17,C7>13),"! Check With TD !", IF(OR(C6>=8,C7>=6),2, "later"))

C. and finally the result '1' - no more IFs needed, as all other cases are already handled:

=IF(OR(C6>17,C7>13),"! Check With TD !", IF(OR(C6>=8,C7>=6),2, 1))

Now if you'd rather use AND (which I think makes it a bit more complicated logically), you could use:

=IF(AND(C6<8,C7<6),1,IF(AND(C6<=16,C7<=12),2,"!Check With TD!"))

which is identical in result.