With if you can check which key the person press or which key (or keys) are not pressed

Code:
var key_s_counter = 0;

if(key_s && !key_w) // if key_s is true (key_s == 1) & key_w is false (key_w == 0)
 key_s_counter +=1;



I dont know what you want to do.
Please write more about your problem.