converting from system::string^ to char* problems

[vcbytes]

I am having a problem with the following code:

System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {
     String^ texts = textBox1->Text;
     char *text = strToChars(texts);
     String^ shiftcs = domainUpDown1->Text;
     char *shiftc = strToChars(shiftcs);
     int shift = atoi(shiftc);
     char *cipher = encCCipher(text, shift);
     String^ ciphers = gcnew String(cipher);
     textBox2->Text = ciphers;
}
...
char* strToChars(System::String^ str) {
     msclr::interop::marshal_context ^ context = gcnew msclr::interop::marshal_context();
     const char* chars = context->marshal_as<const char*>(str);
     return (char*)chars;
}
...
char* encCCipher (char *plain, int shift) {
    char lowerAlphabet[26] = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
    int len = strlen(plain) ;
    char *cipher = plain;
    char cchar = NULL;
    int ccode = 0;
    for (int i = 0; i < len; i++) {
        cchar = tolower(plain[i]);
        ccode = NULL;
        for (int j = 0; j < 26; j++) {
            if (cchar == lowerAlphabet[j]) {
                ccode = j;
                break;
            }
        }
        if (ccode != NULL){
            cipher[i] = lowerAlphabet[(ccode + i) % 26];
        } else {
            cipher[i] = cchar;
        }
    }
    return cipher;
}
 

Entering "Testing cipher" into textbox1 puts out "tfuwmsm krzsqe."
After pressing the button the variables have the following in them:
texts: "Testing cipher"; text: 0x007B6B78 "tfuwmsm krzsqe"; shiftcs: "0"; shiftc: 0x007B6BC8 "0"; shift: 0; cipher: 0x007B6B78 "tfuwmsm krzsqe"; ciphers: "tfuwmsm krzsqe"
So I'm pretty sure the problem is in the converting the input from the textbox to a char* array.
And if you are wondering, this is a Caesar cipher program.
This is c++ code compiled on visual c++ express 2008 on vista.

[vcbytes]

Never mind, I figured it out. The problem was in the for loop.

char* encCCipher (char *plain, int shift) {
    char lowerAlphabet[26] = {'a','b','c','d','e','f','g','h','i','j','k','l','  m','n','o','p','q','r','s','t','u','v','w','x','y'  ,'z'};
    int len = strlen(plain) ;
    char *cipher = plain; //should be "char *cipher = new char; strcpy(cipher, plain);"
    char cchar = NULL;
    int ccode = 0;
    for (int i = 0; i < len; i++) {
        cchar = tolower(plain[i]);
        ccode = NULL;
        for (int j = 0; j < 26; j++) {
            if (cchar == lowerAlphabet[j]) {
                ccode = j;
                break;
            }
        }
        if (ccode != NULL){
            cipher[i] = lowerAlphabet[(ccode + i) % 26]; //"i" should be "shift" 
        } else {
            cipher[i] = cchar;
        }
    }
    return cipher;
}