Help !!

When I'm using the format cells - number tab - categorie "custom" function
to an entire column; I enter format codes (####-#####-#) then select OK
button.
The existing data (1234567891)(no dashes) does not appear in each cell
within the column; not until I edit each cell (F2 or double-click) and hit
enter does the format appear. How do I make the format appear without going
to each individual cell?