Cursor Problem / Toggle Lock and Unlock

Hey guys.

I am currently trying to unlock and lock the cursor.

What I mean by this is.... When the ‘Tab’ button is pressed. It will display the inventory for my player. Which will then unlock the mouse, to allow interaction with the inventory. Then when ‘Tab’ is pressed again, I want it to lock the cursor again...

How do I do this?

I have managed to make it unlock when the player presses ‘Tab’ but I can’t seem to find a way to lock it again when the same button is pressed again.

Please help!