Negative Value should be Positive Value when Automatic Range define

Dear sir / Madam

If A5 column change the value than Range also be changed based on A5 Value and Average Value to be mention in B5 Column
For Example A5 Column Shows 18800 than Range to be select as Column B29 to B52 and answerd should be 91.25
If A5 column Shows 18600 than Range to be select as Column B25 to B52 and answered should be 92.32
Negative and Zero Values in Product Value column should be consider as Positive Value

Note Negative value should be calculate with Positive value When Range found any Negative Value (in our sheet B36 shows -80 value. when calculation done it's should be consider as positive 80