I am trying to count no of nights (not days) for example stayed in a hotel,

For example
You put in the dates in row 1 (A:AA)
Fill then row 2 (A:AA)with "x" if stayed at hotel

Need then another cell to calculate the number of nights that has been
stayed at the hotel (the cells filled with "x").

eg. I need the number of nights between the dates, eg 3 days = 2 nights
between 11th March - 13th March.

Can anyone help?

In advance thanks for your help