perform a calculation on subsets of data of varying length

I have a dataset that is sorted by Part Number (column A). For each part number I have some times listed in days (columns C & E). At each break in part number I would like to perform a set of calculations (columns H through L). The calculation desired is listed in the column header. Column L is the real "magic number" -- columns H through K are means to an end.

Due to the varying lengths of the subsets (i.e., PN 101853 has 2 rows; PN 104537 has 15 rows) I haven't been able to write a macro to successfully perform the calculations for each subset. Additionally if a line only has one record, the number in column L will be zero (you cannot have a standard deviation of one data point).

Please help me!