Here's the copy of
GMExcel Online
It's a very simplified version of the tool that's linked here normally. But this will give your entire league a variable salary cap every year. It's baseline is $100 million, but you can save a copy of the file yourself and make your own personal tweaks and download the xls file to use in your own Calc/Excel program.
It also provides for playoff shares. It has a lot of flexibility and you can make tweaks pretty easy, too.
With a new version of OOTP out, thought it might be handy to share.