How can I change a block's state?

Hallo!

I am trying to create a function triggered by right clicking with a specific item. (I managed to do that, suprisingly lol)
This function contains an "if" statement that checks if a local variable is equal to 1. If it is, another "if" statement checks if the block looked at is an iron door (this works, for sure). Here's when I encounter my problem.

I would like to make it so the door's open / closed state is set to open if the condition above is true. But... I don't know how to do that!

Could someone help me, please? =)