#REF! is a error type which occurs when a cell reference (cell reference: The
set of coordinates that a cell occupies on a worksheet. For example, the
reference of the cell that appears at the intersection of column B and row 3
is B3.) is not valid.
Click the cell that displays the error, click the button that appears , and
then click Trace Error if it appears. Review the possible causes and solutions
(Taken from MSExcel help)
