Odd question, maybe impossible. Lewis And Clark Cipher!!!!

So, the lewis and clark cipher is a key word cipher that i was hoping to figure out a way to do it in a simple manor that doesnt involve text being promoted variables then changing hem to integrs, doing some math then converting back to intergers then translated to a ‘output’ text that you can then copy and paste for moving to different programs.

the cipher is super simple : Key word:Artichokes since both the KEY word and Encryption is an INput, and will be copied and pasted into the input boxs, the Output box needs to be copied as wel
decrypted message:hellothere

anyone have an idea as to how this could work out in a simple fashion?