i would like to have a formula that reads a vba function
some thing like

=varAnaly(rng1 as range,rng2 as range,proof as range)


function varAnaly
if range(rng1) is a number ' is there a NAN in VBA?
and if range(rng2) is a number then

test1 = (range(rng1).value + range(rng2).value ) /2


varAnaly = (test1- proof)/proof

end func

i am having trouble with if its a # and how to write a vba function and use it as an excel formula

Take a look at the IsNumeric VBA function, it'll return true for numbers.

What other difficulties are you having?

Got it all, thanks !~