I need help with excel in python

I have two excel files. One file(a) has only one sheet with columns like product name, minimum value, maximum value and halo value for those min and max values. In another excel file(b), I have 10 sheets where there is a halo column too in each sheet except last sheet. I need a code where the halo value in 'b' file gets updated automatically using the minimum and maximum values in file 'a'. For example, in file 'b', there are columns like product name, list price, lm% and halo. If I change list price, lm% gets updated automatically but halo remains the same. So, we need to take halo from file 'a' where if the min and max values are between 0.5 to 0.7 then halo value is 0.05.