Primitive easy cipher

[MyEarth]

I'd like to make an easy number cipher, pratically just add N number to the final result

My attempt:

$sReturn = ""
$sText = "0123456789"
$nPos = 3
$aSplit = StringSplit($sText, "")
For $i = 0 To UBound($aSplit) - 1
    Select
        Case Number($aSplit[$i]) < 7
            $sReturn &= $aSplit[$i] + $nPos
        Case Number($aSplit[$i]) = 7
            $sReturn &= 0
        Case Number($aSplit[$i]) = 8
            $sReturn &= 1
        Case Number($aSplit[$i]) = 9
            $sReturn &= 2
    EndSelect
Next
ConsoleWrite($sReturn & @CRLF)

I don't know how to make the number start from zero if is bigger the 9, i can't make the case like the example because work only if $nPos = 3
Thanks

[JohnOne]

Please explain a bit more "I don't know how to make the number start from zero if is bigger the 9, i can't make the case like the example because work only if $nPos = 3"

and exact goal of script.

[MyEarth]

Ok

I want to add a number to another number, in the example the position are three, but is a variable and this value can change so:

0 = 3 (0+3)

1 = 4 (1+3)

2 = 5 (2+3)

But when it come the 7

7 = 10 (7+3)

Is wrong, the number are only ten and the max value is 9, so need to start from zero:

7 = 0

8 = 1

9 = 2

So explected string is, if the position to move are three:

0123456789 = 3456789012

Is clear?

Oh, i need to reverse the process too

Edited October 6, 2014 by MyEarth

[Gianni]

using Mod() could do

$sReturn = ""
$sText = "0123456789"
$nPos = 3
$aSplit = StringSplit($sText, "", 2)
For $i = 0 To UBound($aSplit) - 1
    $sReturn &= Mod($aSplit[$i] + $nPos, 10)
Next
ConsoleWrite($sReturn & @CRLF)

[MyEarth]

Thanks

[MyEarth]

Wait, and for reverse the process? 

Come back from 3456789012 To 0123456789

Edited October 7, 2014 by MyEarth

[Gianni]

Wait, and for reverse the process? 

Come back from 3456789012 To 0123456789

this could do ...

$sReturn = ""
$sText = "0123456789"
$nPos = 3
$max = 10 ; (0-9)
;
; forth
$aSplit = StringSplit($sText, "", 2)
For $i = 0 To UBound($aSplit) - 1
    $sReturn &= Mod($aSplit[$i] + $nPos, $max)
Next
ConsoleWrite($sReturn & @CRLF)
;
; and back
$aSplit = StringSplit($sReturn, "", 2)
$sReturn = ""
For $i = 0 To UBound($aSplit) - 1
    $sReturn &= Mod($aSplit[$i] - $nPos + ($max * ($aSplit[$i] < $nPos)), $max)
Next
ConsoleWrite($sReturn & @CRLF)

Edited October 8, 2014 by Chimp