Consult a qualified structural engineer to find out what's needed for support. There isn't any other satisfactory way to do that.
I don't know what windows have to do with the support, unless they're the type that hold the brickwork up. Nor why you need to replace them, more info might help with looking at other options.
Do yourself a favour and come here to uk.d-i-y via a sane portal, not that hopelessly broken page you're using now.
NT