How do I select an Boolean Variable froam an value of another variable?

Hi, i have a little problem. How can i select an bollean variable from an value of another variable? If crafteditem = knife then set player.knife to TRUE?

I can do it manually :

If crafteditem = knife then set player.knife to TRUE

If crafteditem = axe then set player.axe to TRUE

If crafteditem = bow then set player.bow to TRUE

but how can i set it automatically?

If crafteditem = [X] then set player.[X] to TRUE?

Thanks a lot for help ;)

up please