I have a multitab spreadsheeton sheet 3, i use the formula  =SUM(N1:N7)    in N8 of Sheet 3

i want to insert data fron cell I13 on Sheet2, into Sheet 3, Cell N6, but Cell I13, Sheet 2 also has a formula of   =(R13-Q13)+1

I do not have to use this calculation from Sheet 2 all of the time, sometimes, it remans blank, so how can i get the dta to sheet 3, even if the dtat is blank on sheet 2?

So far, if it remains blank in sheet 2, then sheet 3 shows   #VALUE     in Sheet 3, N6 and the Sum in sheet 3 which is located in N8 of Sheet 3 also shows   #VALUE    and will not calculate the SUM of N1 through N7