Automating content insertion based upon existing data values

I have a large spreadsheet which contains certain key values in a designated column. What I would like to do is insert new line items and insert them with specific content as follows: At the end of each group with a fixed value in Column A, after the last of the rows with the same value in Column A, I want to insert two rows. In the first row, I want the value of Column A to be that of the previous row in Column A f(in essence the value of column A for that group) and the ColumnD value to be 'footer', and in the second row, Id like the value of Column A to be the same as ColumnA of the following (next/subsequent) row (group) and Column D to be the value of 'header' . In essence, I am inserting a header line item and a footer line item around each set of Column As of the same value. All the line items are groups together by their value of column A and are in essence, unique.

I have attached a spreadsheet example. with reference to this spreadsheet, there are both before and after worksheet pages where orange line items represent the first instance of a new column a value and the green and yellow line items are those that are inserted....I only need to populate Column A and D for these rows, the rest I can take care of afterwards. If there is an issue for the very first and last groups in the worksheet, I can address this manually, that is not an issue, but since there are 1000s of line items and hundres of groups, I want to figure out a more efficient manner for the bulk of the sheet.

Any help would be gratefully appreciated. This forum has been very helpful in the past to me.

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