Shift numbers down sequentially in a column

I have a column that organizes my tasks (rows) by priority. So, my highest priority is 1 and my lowest is 10, etc. When I add a new task to the spreadsheet and I decide that it is now the highest priority, I want to put 1 in the "Priority" column and then everything else in that column goes down one number sequentially. So, what was previously 1 in priority is now 2 and so on. Is there a way to do this?