You can put the cut points in a macro and do something like, for 3 industries
local cuts "4 7"
gen ind=""
local i = 0
foreach c in `cuts' {
local i = `i'+1
replace ind=char(64+`i') if id<=`c' & ind == "" & id!=.
}
local i=`i'+1
replace ind=char(64+`i') if ind == "" & id!=.