Check Digit Generation Formula

[hemeraser]

Working on generating a few thousand SSCC codes.

The code is 17 digits plus a check digit. For instance 00813590020000000 should return 008135900200000002.

The check digit is calculated by this process:

I found a formula on these forums that calculates 13 digit codes but have came up short using Google to find a formula for what I need.
The formulas I found are:

=A2&(10 -MOD(SUMPRODUCT( MID(A2,ROW(INDIRECT("1:"&LEN(A2))),1)*((MOD(ROW(INDIRECT("1:"&LEN(A2))),2) =1) +3*(MOD(ROW(INDIRECT("1:"&LEN(A2))),2) =0))),10))

Any help would be appreciated.

 

[oldbrewer]

sum of the multiplications is 68
add 5 = 73
integer(73/10) = 7
7 *10 = 70
70 - 68 = 2