Looks as though even prior to Excel 2007, there are no real shortcut keys like there are in MS Word for Left/Center/Right align. Was just looking at my Windows Default Key Codes file with the different combinations of modifiers for the Windows platform, and nothing is in it for these specific items. One reason why I created such a file was to help make data entry a bit easier, especially if one is using the 10-key numpad (MS calls it keypad, but numpad makes more sense in my mind as the terminology I learned long before I saw MS calling it keypad). That's because I was toying with events like KeyPressDown to trigger certain actions. However, the problem with that, VBA can't distinguish between the different keys such as the Enter Key on the QWERTY vs the Enter Key on the numpad, when using the Key Scan Codes. It would require a programming language like C programming or C#.NET to decipher between the different keys, including which Alt Key was pressed and of the like.
Another reason for me to create this file was also to see which keyboard combinations are not being utilized, which then allows me to assign macros to such unassigned keyboard shortcuts.
One such site that has a list of keyboard shortcuts for Excel 2003 is
http://www.shortcutmania.com/microsoft-excel-2003-keyboard-shortcuts.pdf However, there is nothing listed in there for cell alignment purposes.
If you had to do it via keyboard, guess you could do Alt,O,E and then use the Ctrl-PgDn to get to the Alignment Tab, and use the accelerator in there to get it right aligned. That's one thing that MS did make a bit easier with 2007 and beyond, using the Ribbon accelerator keys (i.e., Alt,H,A,C for Horizontal Center of the cell), though I hate the size of the ribbon to the point with certain files, I have to hide it via the Ctrl-F1 keyboard shortcut. However, if you have the old toolbar keyboard shortcuts memorized to 2000-2003 versions of Excel, you can still use that too within Excel 2007 and later (i.e., Ctrl-C,Alt,E,S,V,Enter, or use Ctrl-Insert in place of Ctrl-C to convert the selected cells from formulas to values, or use Alt,E,A,A to clear everything including formats within the selected cells)