Entering a number into two different textboxes

Hey all,
I’ve been scratching my head on this for a little too long.

I have two input text boxes. I need to enter a number (1900) into the first box then hit the ‘Enter’ button, then enter a number (50) into the second box right below the first.

After the ‘Enter’ button is pressed it needs to lock-in the required value, by selectable = false.

My problem is…I can get the first number to work. I type in the number, press ‘Enter’, it changes the textbox value to selectable = false…everything is good for that part.

But the second number is where I am having trouble, it seems the function is called, but that’s it…nothing else happens.

Any help is greatly appreciated.

Note: I have attached the file.