The problem is that I seem to understand what is going on, but at the same time, when I try to do any slight modification (obviously apart from renaming "myserial" to something more relevant) I hit a brick wall...
Every time you hit a brick wall, and need help, you need to post your latest code.
Isn't there an easier way to read the sensors and have that value stored as "new val" so that the arduino can run an "if" statement?
It really isn't that hard to only read the serial data that is present, and wait to act on the data until all the data has arrived.