I have a list of projects in cells A1 through A10. Some project names appear more than once.

I have another list of 3 projects in cells B1 through B3. Each project name in this range in unique.

I need a count of how many cells contain projects that are listed in cells A1 through A10, but are not one of the 3 projects in cells B1 through B5.

For example:
A1 = Project A
A2 = Project B
A3 = Project B
A4 = Project B
A5 = Project B
A6 = Project C
A7 = Project D
A8 = Project E
A9 = Project F
A10 = Project F

B1 = Project A
B2 = Project C
B3 = Project F

The formula should return 6. There are 6 items in the A range that are not in the B range.

How can I do this?