There is no in-built function but you can record a very simple macro to sequentially go down your numbered list. Consider the tasks you want to do. You want to quickly run down your list, move your cursor to the end of each line, and highlight ALL text to the beginning of that line. A macro just stores all these instructions so that you don't have to do them yourself each time. Follow these steps:
- Keep your cursor at the start of a list item (no highlight)
- Go to View > Macros > Record Macro
In the Window that pops up, type in a macro name and select 'Keyboard'

Enter a new shortcut key by pressing the actual shortcut you want (say ctrl+7). This shortcut is safe and won't overlap with any existing Word 2007 shortcuts.

Click 'Assign' and close the window.
The mouse pointer will also have changed to be a pointer with a tape next to it to show
you are recording a macro. Only keyboard operations are permitted. Press the down arrow (to go to the next line), press end to navigate to the end of line, and then use ctrl+shift+left arrow to highlight the entire line.
- Go to View > Macros > Stop Recording. The macro should be saved as is.
To test it, place the cursor anywhere in the numbered list field and press ctrl+7. You should be able to repeatedly jump to the next item in the list and have the entire line fully highlighted each time.
You can create a similar macro (with another shortcut) for navigating upwards in the list the same way. Easy enough, I hope.