need help with the chrW function and handling invalid inputs

[Apocmonk]

At the moment im working on an encryption program, just to prove something to myself. At the moment I have a problem, when I run the program it will drop a few characters and return wrong characters, here is the encrypter code.

        Dim x As Int64
        Dim y As Int64
        Dim z As Int64
        Dim chrpos As Int64
        Dim chrcode As Int64
        Dim str As String
        Dim Buffstr As String
        Buffstr = ""
        str = TBX1.Text
        For z = 0 To 10
            Buffstr = ""
            For x = 0 To str.Length - 1
                For y = -32768 To 65535
                    If str.Chars(x) = ChrW(y) Then
                        chrcode = y
                        chrpos = x
                    End If
                Next
                chrcode = chrcode + ((chrpos * chrpos))
                While chrcode > 65535
                    chrcode -= 65535
                End While
                While chrcode <= -32768
                    chrcode += 32768
                End While
                Buffstr = Buffstr & ChrW(chrcode)
            Next
            str = Buffstr
        Next
        tbx2.Text = str
 

notes:
> tbx1 and 2 are textboxes for input/output

> the difference between the encryption and decryption code is that the decryption is the addition the square of the position of the characters and the encryption is the subraction of the sqaure of the position of the characters

>when I run the code above and encrypt 195 1's then decrypt the output it rerurns

11111111111111111111111111111111111111111111111111 11111111111111111111111111112222222222222222222222 22222222223333333333333333333333334444444444444444 44444555555555555555555666666666666666667耷77耷

the output should be 195 1's but it is as above

in advance thank you for the help

[tlhintoq]

Original Poster: I have xxx, then do yyy then zzz happens. Here's my code ...

Ok. You know what you have.
What you don't have is a question. Nobody here knows why you posted this since you haven't asked anything, or exception or description of any error messages you are getting. You haven't described anything that is broken, or any 'expected' results versus 'actual' results.
I recommend you read the FAQ about How to ask a good question so the volunteers will be able to help

[Apocmonk]

@tlhintoq
I have ammended my question and added the actual and expected results. Tahnkyou for thhe pointers