excel - Change Index range by Cell value -

if put correct range somewhere on spreadsheet, ie cell

name_input!b73

how can use range listed there:

a78:aj118

as range replace a82:aj117 in formula

=round(index('qb class'!a82:aj117,match("4010 · billing",'qb class'!f1:f38,0),match("-billing",'qb class'!1:1,0))/1000,0)

so final result be:

=round(index('qb class'!a78:aj118,match("4010 · billing",'qb class'!f1:f38,0),match("-billing",'qb class'!1:1,0))/1000,0)

and i'd have change cell on sheet name_input change every formula referencing range.

thanks guys

i'm not sure if understand problem, think looking indirect function.
replace 'qb class'!a78:aj118 indirect("'qb class'!" & name_input!b73)