how to determine if variable is set?

Hi

get(variable) should return null, when the variable was not set before. I need to determine if the variable "n" is set or no. In case that not, set(n,0).

<action name="startup">
if (get(n)==null, set(n,0););

....

get(n)==null returns as false even if n was not set before...

any ideas what do I wrong? thanks

thanks a lot. works fine :)