I am trying to create a customized function.When ever I use cosh or sinh or
ln .. function within a formula I get a compile error. Sub or function not
defined.

sample code

Function tg(number)
tg = Cosh(number) + Sin(number)
End Function

I get no error when I use this code but with simple sin and cos

Function tg(number)
tg = Cos(number) + Sin(number)
End function

any ideas why this happens ?

Thanks in advance

ravi