Add New Check Digit Follow

I would like to add my own check digit under Data Source -> VB Script -> category -> Functions and check digit. I looked in my local drive for where these check digits are stored and can not find them to add my own version. We have multiple check digits that we would like to program in and be able to pick a certain one for certain jobs rather than copying and pasting the VB Script every time. Could you please help how I can add my own scripting.

Here is one example of code that I am using:

Mod 7DR
dim var,var2,mod7
var = value/7
var3 = FormatNumber(var,3)
var2 = mid(var3,Len(var3)-2,2)
if var2 = 14 then
mod7 = "1"
elseif var2 = 28 then
mod7 = "2"
elseif var2 = 42 then
mod7 = "3"
elseif var2 = 57 then
mod7 = "4"
elseif var2 = 71 then
mod7 = "5"
elseif var2 = 85 then
mod7 = "6"
elseif var2 = 00 then
mod7 = "0"
end if
value = value + "--" + mod7