Calculating Slope and Intercept with a changing number of data points

Hi,

I would like ot be able to calculate the slope and intercept of a best fit line. This spreadsheet will be used as a template and the number of data points required for the analysis will change from each data set. I would like to be able to type in the number of cells to be include as opposed to manually changing the formula each time I insert a new set of data.

I have attached a spreadsheet to let you know what I am roughly after.

Any help is much appreciated.

Cheers,

Andy

Slope Intercept Spreadsheet.xlsx