How to split rows of data when there is a break in consecutive numbers?

[HowellsRailway]

I am having trouble separating data in Excel and would appreciate any help.

The data is taken from a datalogger and has been exported into excel via a CSV file, it was then filtered and copy and pasted into a new spreadsheet which now needs putting in to a graph.

In column A i have a run of sample numbers (in 100s of milliseconds) and in column B i have a continuous run of data all equaling 1.5 (the 1.5 value is irrelevant, i am more interested in the count)

I have 108 'blocks' of data, i.e from cells A273-A337, i have a count of 64. Then from there it jumps straight from A556-A620, a count of 65. A840-A903 is another 'block' of 63 etc, this continues 108 times. I basically need to separate each block of data and count how many rows are in each block, from there i need to enter the data in to a line graph and take an average of the count (will be approx 64). I am confident in converting the data into a line graph, it's just the separating of each block of consecutive numbers i am struggling with.