Joining selected records from a table

I have created a table by importing a CSV file of stockmarket data.

The table has a set of fields.  These are date,turning point type (High or Low),Primary Turning Point price, Secondary turning point price and tertiary turning point price.  The Primary and Secondary Turning Points are often zeroes for the record is for a tertiary turning point.

I have created tables for each turning point type but he records here are a "join" of two records from the first file.  The records is Start Date, TP_Type, Start Price, End Date, End_TP_type, End_Price.  I want to select the first non-zero Primary Turning Point, and create a record for each later non-zero primary turning point adding a duration in days and a difference in starting price and ending price.  Once the first cycle through the file is achieved then I want to move to the next non-zero primary turning point record and go through the table again.  This continues till all records have been processed.

How can I achieve this as my starting table has 16,500 records.  I understand this will take some processing time.