Average Mortgage Balance

[Mike6174]

I have a mortgage balance in January of of the year of $1,000,000. Paid down a significant part of it in February (still the same mortgage). So the current balance is less than $750,000. But the average balance is far less than beginning of year + end of year balance divided by 2.  I can calculate the average balance by averaging all of the months (accepted by IRS) but how do I get this into TurboTax to calculate the fair mortgage interest deduction (desktop premier version)?

[Mike9241]

in box 2 on the 1098 enter the average balance you have computed

when or if your asked about the year end balance use the number above

not supported in Turbotax 

Someone who wants to use another method of averaging loan balances other than the beginning and ending balance method.