Use formula for blank data in get excel rows

[dpimart]

I have 2 separate excel workbooks, each with 1 table. 

Sheet1 table1 copy/pastes to Sheet2 table2 data.  

I have monthly columns in each table and the data from each in ST1 gets copied over into the matching rows and columns of ST2. 

However, if there are still months remaining in the year, then there will not be any data in ST1 to be copied over.  In that case, I need those blank month columns of ST2 to be a calculation which would be ((Plan - YTD Actuals) / # of remaining months).  

How do I add this in??

[SudeepGhatakNZ · Accepted solution]

Assuming they are both date columns, you could use the dateDifference function. It returns a Time span.