how to edit =sum(..)

[bill lam <cbill lam gmail com>]

When type "=sum(" in a cell, it allows me to use arrow keys to select
range of cells. However when I press F2 to edit that formula again, it
seems impossible to use arrow keys to select a new range of cells
again.  Does it mean "=sum(" have to be typed again for selection?

-- 
regards,
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