hey i have 3 series. each is a formula. example:

series 1 in column b
iferror(((sheet2!B4/sheet2!B5)*1000000),0)

series 2 in column c
iferror(((sheet2!B2/sheet2!B1)*1000000),0)

series 3 in column d
iferror(((sheet2!B2/sheet2!B5)*1000000),0)

i need next columns in series to increase letter by 1 for each series

so i need

series 1 in column e
iferror(((sheet2!c4/sheet2!c5)*1000000),0)

series 2 in column f
iferror(((sheet2!c2/sheet2!c1)*1000000),0)

series 3 in column g
iferror(((sheet2!c2/sheet2!c5)*1000000),0)

and then

series 1 in column h
iferror(((sheet2!d4/sheet2!d5)*1000000),0)

series 2 in column i
iferror(((sheet2!d2/sheet2!d1)*1000000),0)

series 3 in column j
iferror(((sheet2!d2/sheet2!d5)*1000000),0)

and so on for 40 times. havent been able to do it. keeps increasing by more than 1 letter. any help is appreciated.