worksheet function - Excel: How do I get a dynamic formula which can display a total of unique values in a range?

Example range:

A10=100, 
A11=105, 
A12=100, 
A13=100, 
A14=7, 
A15=105.  

The formula I need would display "3" only as there are only 3 unique values in this set. The spreadsheet will be updated to add more values as needed in the column "A". Blanks should not be included in any total.

Answer

From here:

=SUM(IF(FREQUENCY(A10:A1000,A10:A1000)>0,1))