return data in cell to right of 2nd to last data entry in column

I have a column of numbers. I use a macro to insert data at the end of the column. I want to subtract the second to last number from the last number and divide the total by the data in the cell adjacent to the last cell. This is what I've done so far.

=(LOOKUP(9.99E+307,Logs!A:A))-INDEX(Logs!A:A,AGGREGATE(14,6,(ROW(Logs!A:A)-ROW(Logs!A1)+1)/(Logs!A:A<>""),2))

It gives me the difference. Now I need to divide this difference by the cell adjacent to the last.

I wrote it like this and the results are invalid

=(LOOKUP(9E+99+307,Logs!A:A))-INDEX(Logs!A:A,AGGREGATE(14,6,(ROW(Logs!A:A)-ROW(Logs!A1)+1)/(Logs!A:A<>""),2))/(LOOKUP(9E+99+307,Logs!B:B))

Can someone please help