Selecting a range of consecutive cells within a range

Hi everyone,

I'd like to try a different approach to counting the amount of days in a period.

If I list a long consecutive series of cells with days in a consecutive sequence in excel and then have two cells put aside for the first and last date in the desired range to be manually entered then is there a way to use the Countif function to select this desired range within the long range?

On the example attached I would like to see if it's possible to build a formula to pick up the values entered in F1 and F2 and then find these dates in the range of cells on the left and count the cells between the two dates inclusive (the answer here would be 15).

I would be grateful if anyone can suggest a way to this.