Inserting copied rows (some locked cells, some not) in a protected sheet

I've spent the afternoon searching the forum, and I haven't found a solution to my current problem. I would appreciate any help anyone can offer.

I have a simple spreadsheet, protected to prevent accidental override of formulas. Each row has formulas (locked) and input cells (unlocked).

I have several rows of data with a sum below, but I'd like to keep 2 unused rows (with locked formulas, but without inputs) between the last data row and the sum. Additional rows are often needed. Rather than simply "insert rows", I want to be able to copy the first unused row and insert the copied cells just above that row, so that the new row has all of the same formulas and there are still 2 unused rows between the data lines and the sum. I have no problem copying, but the sheet protection prevents me from inserting the copied cells.

Users of the sheet need this copy/insert ability, but they will not have the capability to unprotect the sheet. Is there code that I could add to the sheet that would allow this action without unprotecting the sheet?

Thank you!