Named Event Rule terminate execution

I am designing a named event rule and doing validation at the beginning. 

I am checking values so they exist.  The way I've exited the NER if to nest if statements, but I am wondering if there is way to stop execution completely without having to use nested if's

Example

Current Method

IF (something exists) 

    IF(somethingelse exists)

        //begin execute of program

    Else

   set datastructure value to indicate invalid data

Else

set datastructure value to indicate invalid data

disadvantage to this is that you can get pretty deep quickly with if statements

Preferred Method

If(somethingIsNotValid)

    stop execution

    set datastructure value to indicate invalid data