SetByteAt
BString& SetByteAt(int32 pos, char to);
value.SetByteAt(offset, '0');
value.SetByteAt(firstDigit + decimalSeparatorWidth, '0');
value.SetByteAt(offset, char(digit + 48));
result.SetByteAt(i, '%');
name.SetByteAt(i - spaces, ' ');
outString.SetByteAt(lastDot, (char)diff);
outString.SetByteAt(lastDot, (char)diff);
outString.SetByteAt(nextDot, '.');
string.SetByteAt(0, 'a');