I am not sure why a command button would be necessary to do this. You can do this with a simple box (Insert > diagram > rectangle). Type some text in the box, like "click here" and then press CTRL+K. In the dialog, select the workbook you want to open.
Whether sheet is hidden or not, the references are still valid. So it would work (provided you are able to type in the reference in the hyperlink box) I am not sure about the behavior though... you can give it a try.