To lock most cells, select the cells you want unlocked, unlock them, then protect the sheet. To unlock most cells, select all cells, unlock them, then select and lock the cells you want protected before protecting the sheet. Both processes involve unlocking cells, selecting cells to lock/unlock, and then protecting the sheet with an optional password.

1. If You Want the Majority of Cells Locked
To lock the majority of the cells on the worksheet, follow these steps:
Select the cells that you want to remain unprotected.
On the Format menu, click Cells, and then click the Protection tab.
Click to clear the Locked check box and click OK.
On the Tools menu, point to Protection, and then click Protect Sheet. Type a password if
you want one, and then click OK.
If You Want the Majority of Cells Unlocked
To leave the majority of the cells on the worksheet unlocked, follow these steps:
Select the entire worksheet by clicking the Select All button (the gray rectangle in the
upper-left corner of the worksheet where the row 1 and column A headings meet), or by
pressing CTRL+A or CTRL+SHIFT+SPACEBAR.
On the Format menu, click Cells, and then click the Protection tab. Click to clear the
Locked check box and click OK.
Select the cells that you want to protect.
.
On the Format menu, click Cells, and then click the Protection tab. Click to select the
Locked check box, and then click OK.
On the Tools menu, point to Protection, and then click Protect Sheet. Type a password, if
you want one, and then click OK.