Update AR invoice Header

Is there a way or possible to update what is displayed at the top of the AR invoice screen? If someone can just let me know if possible and where to start.

I would like to add additional information at the top where I marked with a red box.

Basically accounting would like to see not just the total but remaining balance (if we have one)

Please see screen shot.

You can edit the Tab page in Application Studio
image

and add a numeric box or something to that space:

Thank you.