Insert Row Macro

I would like to find the code to make a button in excel, that when clicked, will insert a new row into the last row of a section so that the formatting is the same as a sample of other rows in that section, but it will be clear of data and only contain the correct formatting. I would also like this code to make a sum formula in a cell below the newly inserted row to change and to include the new cell within its formula.

For example:

I have a form on excel that has space for 6 rows of data with 3 pieces of information (which are: item, section, cost). If / when I need to add a 7th line I have box that I would like to assign a macro to so that when I click on it, it adds a 7th line with the same formatting that can be found in rows 1-6 but will be void of data. However, under the 6th row I have a total of the 'cost' with an '=sum(D7:D12)' formula and any other code I have found and have used it does not automatically tell the formula to add an additional cell to its summation to make it =sum(D7:D13).