Cells that can change date depending on the number i put in

I put number 1 in c16, the cell highlights red, put a number 2 in cell c17, the cell goes orange and 3 in cell c18 the cell goes green
i fill out the rest of the info

now i have put in a date rasied, now the due to be completed needs to be plus 7 days for the red, plus 14 days for the orange and plus 21 days for the green
but i need it to change depending on what number i put in column c

next when the completed date has passed i need it to put a date in column k next to the item counting up the dates it has gone past, but then take the number away if the status has closed


Action Status Report - Copy.xls hope you understand

yeah thanks humdingaling
but could it be done so that if i put a date in the completed on column, it hides or deletes the date in overdue column and changes status to closed

how do i put some data in cell k4 and then get it to show only the rows that have the same data in.

eg: c2 in k4 then only show the c2 in column d and the rest of the data in that row, but hiding the rest