Time on Duty, make cell blank unless reference cell in formula has data.

I am trying to format a spreadsheet to show the time a vessel came on duty, then show the current time and have the third cell calculate the time on duty in hh mm. I have no trouble getting this to work but, the spreadsheet fills in the two columns that hold calculated data. They are the Current Time and the Calculated Time on duty.

I want these two columns to stay blank unless the first column Time came on duty has been filled in.

Please help, have no hair left already.

Thanks

Bill

Hi and welcome to the board

If time came on duty column is , say col A, enter something like =IF(A1="","",your_formula)