Custom keyboard and type letters

Question

Hi , every one i create custom keyboard and i have problem iam using my keyboard as textview.inputView = myKeyboardView; my keyboard buttons have this code :

NSMutableString *text = [textPad.text mutableCopy];
    NSRange selectedRange = textPad.selectedRange;

    [text replaceCharactersInRange:selectedRange withString:@"A"];
    textPad.text = text;
    [text release];

so the problem is when i want edit a word from middle of my sentence if i select a word and add some letters to that my button write only ONE Character and if i write some other letters that begin end of sentence ! what can i do to solve this problem ?

//EDIT//: PROBLEM SOLVED