Need Help :)

hi im new here

sorry bad english...

im making program opens cmd access internet modem , change mac address problem when put mac address on textbox need last digit add +1. letters or numbers 

for example: ill put c8:d1:5e:24:5a:ec on text box , result be c8:d1:5e:24:5a:ed ill wait replies in advance

here:

  sendkeys.send("sncfg dset wan_mac" + (" " + textbox1.text));
            sendkeys.send("{enter}");
            system.threading.thread.sleep(500);
            sendkeys.send("sncfg dset lan_mac" + (" "+textbox1.text));

i need add +1 last digit ive put on textbox lan mac..

idk why not working says numberstyle not exist in current context im new in visual studio :d

c# 

add beginning of file:

using system.globalization;

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