like this:

My ASCII Chart

    0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
0  NUL SOH STX ETX EOT ENQ ACK BEL BS  HT  LF  VT  FF  CR  SO  SI
1  DLE DC1 DC2 DC3 DC4 NAK SYN ETB CAN EM  SUB ESC FS  GS  RS  US
2   SP  !   "   #   $   %   &   '   (   )   *   +   ,   -   .   /
3   0   1   2   3   4   5   6   7   8   9   :   ;      ?
4   @   A   B   C   D   E   F   G   H   I   J   K   L   M   N   O
5   P   Q   R   S   T   U   V   W   X   Y   Z   [   \   ]   ^   _
6   `   a   b   c   d   e   f   g   h   i   j   k   l   m   n   o
7   p   q   r   s   t   u   v   w   x   y   z   {   |   }   ~ DEL

I want to call a function, alter the ascii sequence in this function and when it return, the ascii sequence back to the original.

thanks in advance!