Finding the average based on the filtered criteria

Hi!
Im quite new into programming so i need some help with Building a macro.
What i need it to do is:

1 Apply filter on data sheet, to filter out type of products (i.e. if product type is A, apply Product type = A)
2 filter out "NIL" and "Timing is irrelevant" under Timing Category
3 Sum up the time difference (mins) based on the filtered criteria
4 Sum up the total number of transactions under product type A
5 At coloum B8:C8, apply formula of (total time taken / total transactions)
6 Clear the filter at data sheet
7 apply the filter criteria of step 1 and 2 for product B
8 Repeat step 3-5 for product B, but the formula for product B is applied at D8:E8
9 Clear the filter at data sheet
10 do the same for Product C and D
11 clear the average timing whenever there new data being pasted into data sheet