programming question



Hello,
 Suppose I have a real function f(x) of a a real variable x and a list, 
say list_a of 1000 real numbers.
I know that on some numbers , x_0, in 'list_a' the evaluation f(x_0) 
produces numerical overflow, but on others it does not. 
 I would like to produce a sublist, list_b, of list of the numbers, y,  
on which f(y) is less than 10^6. 

 I want to know how to find list_b. 

When I try to test each value in list_a, my program stops as soon as an 
overflow is reached.  How do I tell maxima to record that an error was 
produced and keep on going?

TIA,
 -sen