Create conditional formatting for excel file

Required: 1. Highlight rows containing multiple copies of a particular invoice number. eg an invoice's details may be display on 2 or 3 rows. These rows will be highlighted in light blue. Alternate groups of rows need to be highlighted a different colour (see examples attached eg Row 2 has the invoice displayed only once so requires no highlight, Rows3-4 has the invoice displayed 2 time, rows 5-7 has the invoice 3 times. ) In column H the total products value for that invoice number is required displayed on the last row containing that particular invoice number. The formula/rule will be needed so that it can applied to new worksheets or clear instructions provided on how to implement the necessary formulas.