A B C
FD 1 1
EA 1 1
FD 2 2
FD 2 1
EA 2 1
FD 1 2
EA 1 2
EA 2 2
FD 2 1
FD 1 1
EA 2 1
FD 2 2
FD 3 2
EA 2 2
FD 1 2

Based on the table above, is there a formula to count the number of times
"FD" has a positive and/or zero total in sequence? (i.e. when formula detects
the text "FD", it calculates column B - column C = + or 0 total)

The table is updated 2 times a week so the row will keep adding. In the
above table example, the formula should return 4. This is because:
a) FD appeared 3 times with + or 0 result (row 1,3 & 4 before a break with
-result in subsequent FD appearance), then;
b) FD appeared 4 times again with + or 0 result (row 9, 10, 12 & 13 before a
break again).

What is the best way to calculate this?