Trending formula and indicators

Hi - Currently looking at a KPI dashboard. Specifically looking for a formula/function which will calculate the trend of historic data and then represent that as a trend indicator (using conditional formatting).

Attached a small data sample. So looking to do 2 things...

1. Return a value in cell N2 which has calculated the trend of the costs for the past 6 months of data (H2:M2), or whatever time parameter I wish (I have been round the houses here trying to calculate using SLOPE, INTERCEPT, LINEST, etc); then

2. The practical application of a trend indicator against the trend outcome in N2 (using the 5 directional arrows in conditional formatting Home>conditional formatting>icon sets>5 arrows (coloured) ). On this point I guess I am more after the answer to the question - 'are there more accepted parameters for what constitutes an upward, downward, upward sloping, etc trend, taking into consideration the suggested calculation for N2, and therefore what values should I enter into the conditional formatting rules for the 5 arrows?'

After some helpful reading - I found myself musing over some mathematics papers on line, realized University was too long ago, and it was time to ask for help.

Any suggestions or advice greatly appreciated.

Thanks