I'm thinking this must be in a larger loop structure to keep returning to the routine.

How about this as an idea only:

Code:
If Temperature > Temp_Up then           ' Above Target temperature
  PORTA.2=0                             ' Deactivate Warm output
  PORTA.3=1                             ' Activate   Cold Output
SOUND PortA.7, [107,50]
temp_up = temp_up +5                     'or 10 or whatever
endif                                    'as long as reset elsewhere