For cells you want to enter data into, select the cells, right-click and choose format cells. Select the protect tab and remove the check from Lock cells. Click OK to exit cell properties. Now when you protect the worksheet, the "unlocked" cells will be available for data entry. When you use the tab key the cursor will advance to the unlocked cells and skip over the locked cells. ( all cells are locked by default. you must manually unlok in cell properties
Since you can arrow into them I assumed you could tab into them as well. My bad... thanks anyway.
I think hitting scroll lock on the keyboard does what you want - give it a try
What you are after is DataEntryMode
have a look @ online help.
Ivan