ISBLANK
Tests if the cell is blank (empty).
Syntax:
ISBLANK(cell)
Returns TRUE if cell is a blank (empty) cell, and FALSE otherwise. Cells containing a formula or a error return FALSE.
Example:
ISBLANK(D2)
returns TRUE if D2 is an empty cell, and FALSE if D2 contains a number, text, TRUE, FALSE, a formula or an error.
