If I am reading your post correctly you want a cell to equal C1/D1 when
A1=1
and B1= some some number
and for the cell to = "na" otherwise
=if(and(A1=1,B1=xx),C1/D1,"na")
Just enter your wanted number in place of xx or
you could put the number you want in E1 and use
=if(and(A1=1,B1=E!),C1/D1,"na")
If I am not reading your post correctly, please let me know.
in

"Flutie99" wrote:

How do I write a command that says:

=if(a1=1&b1=a number, c1/d1,"na")

How do I write the "a number" part?