Creating Formula that Adapts to Info Being Pasted into Spreadsheet

Hello,

In Excel I have a table where the rows show different tenants' leases and the columns state when the lease begins ("Lease from"), when it expires ("Lease To") and the Area of that specific lease. If a lease is a month-to-month (MTM) lease then the cell in the "Lease To" column for that specific lease is left blank. In that same spreadsheet I have a second table where the columns are the expiration year of the lease (MTM, 2020, 2025, etc...) and the row is the total area of all of the leases that expire in the corresponding year.

I should mention that some of the rows in the first table also correspond with a VACANT space that has no lease. In this VACANT space row, there is data in the Area column that shows how big this space is, but there is no data in the "Lease From" or "Lease To" columns. This has the potential to create problems when creating a formula for a month-to-month (MTM) lease as I will show below.

For instance, if there were 3 different leases that were MTM in the first table that added up to 7,000 SqFt, I could just insert a f(x)=sum(E5:E7) into the Total Area row of the second table underneath the MTM expiration year. However, I want to be able to create a formula that will adapt to new leases being inserted into the first table. What I am thinking for an IF statement in the second table for MTM leases is as follows:

IF formula in second table for MTM-->IF a cell in the range of selected cells on the first table (under “Lease To” column) has no value in it, then the cell in the second table with the IF formula in it equals the cell (in the first table) in the “Area” column in the same row as the cell that had no value in it (but it must be in a row that has a current tenant, NOT A VACANT SPACE), if a cell in the range of selected cells (under “Lease To” column) does have a value in it (i.e., date) then this cell with the formula in it has no value.

I know what I want my IF statement to do, I just don't know how to write it in Excel. I tried to be as detailed as possible in the above descriptions, any help would be greatly appreciated as to how to write this IF statement.