COUNTAVISIBLE

COUNTAVISIBLE(rgeValues)
Returns the number of visible, non blank cells in a range (including logical values and text).

REMARKS
* This function excludes hidden cells caused by AutoFilter, Grouping or that have been Manually Hidden.
* You can use the built-in COUNTA function to include hidden cells.
* You can use the user defined COUNTVISIBLE function to
* You can use the user defined COUNTVISIBLEIFS function to
* Similar to the user defined functions AVERAGEAVISIBLE, MAXAVISIBLE and MINAVISIBLE

For instructions on how to add this function to a workbook refer to the page under Inserting Functions