COMMON-EVENTING AND PARALLEL PROCESS IS BREAKING MY HEAD.

I'm having issues with common event parallel processes negating on-map events (such as important "on-touch" events).

I'm trying to make a common event that checks my character's HP with a variable and some conditional branches and then changes the character sprite accordingly to represent low health at varying degrees.

First problem (using arbitrary figures and names): I want at least 3 increments, I inititally tried:

Set variable blah to Hero's HP.
Then
"if less than 100, then change to sprite x"
ELSE
"if less than 200, then change to sprite y"
ELSE
"if less than 300, change to sprite z"
ELSE
nothing.

- this doesn't work because all of the ELSE handlers are ALSO below 100 meaning that sprite X will display until the character's HP is more than 300.

My second problem is that I've got all of the above in a common event that is a parallel process (set to activate by a trigger-switch). As soon as this parallel process is running (trigger switch is ON) it negates all event processing on the maps except for "Action key" triggered events.

I've probably gone about this entirely wrong. I could use some advice as to how to make it work without it breaking everything.

EDIT: With help from Cal, Yellow_magic and Shinan I think I've managed to get this working fine now. :) Thanks guys.