Writing code for a feedback loop

I'm having some difficulty writing a routine for a feedback loop. What I need to do is read a value taken from the network. Then I adjust the PWM based upon the value. In laymans terms, it would look like this:

Code:

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IF TEMP > 105 AND TEMP < 170 THEN        'IF TEMP IS IN THE NORMAL RANGE, WE FORCE IT. OUTSIDE NORMAL RANGE, WE DON'T TOUCH IT.
            FORCE_FLAG=1                          'THE FIRST TIME THIS ROUTINE IS ENTERED
            DUTYCYCLE=(170-TEMP/3)+222    'THIS GETS ME IN THE BALLPARK
            FORCE_FLAG=0                          'ROUTINE HAS BEEN ENTERED SO THE FLAG IS NOW RESET AND
                                                          'THIS ROUTINE WON'T BE ENTERED AGAIN UNTIL THE TEMP IS OUTSIDE THE NORMAL RANGE
        ELSE
            FORCE_FLAG=1                          'THE NEXT TIME THROUGH, WE NEED TO CHECK THE INITIAL ROUTINE   
            DUTYCYCLE=0                          'THE TEMP IS OUTSIDE NORMAL VALUES SO WE DON'T TOUCH IT.
        ENDIF
       
        IF FORCE_FLAG=0 THEN                  'THE INITAL ROUTINE WAS ENTERED SO NOW WE NEED TO FINE TUNE IT

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This is where I'm stuck. Between 105 and 170, the PWM range will be approximately 22 steps (222 at 170 and 244 at 105). In the first routine I got the value close but how do I adjust the PWM signal without over or undershooting the perfect value?

I may be over simplifying it but, if the TEMP value is within the adjustment range of 105 and 170, it seems that the IF/THEN condition would fine tune your PWM signal already.
I also notice the DUTYCYCLE math needed the parentheses moved.

Code:

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IF TEMP > 105 AND TEMP < 170 THEN
    DUTYCYCLE = (170-TEMP)/3 + 222
ELSE
    DUTYCYCLE = 0
ENDIF

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