Not sure there is a way to assign shortcuts to activate specific sheets without using VBA unless anyone else has a solution....a couple of ideas perhaps............
A) Open your worksheet and use the macro recorder to record yourself activating the sheets you wish add a shortcut to each one. Although it uses VBA you could always use the Ctrl + XX shortcut keys to access the sheet you require
B) Create a summary sheet at the front of your workbook with a hyperlink to all the sheets within the book.