Trying to add an extra Principal Payment to an existing Loan amortization Sheet?

[Wheelman666]

I DL a Mortgage Template from the Store, and it works for me, mostly. What i am trying to do is on 1st TAB add a box for an additional Principal Only Payment
add into the both the Monthly P&I Payment and into the Total Monthly Payment. Then in the amortization Table make sure that amount is added to the Principal portion of the payment only.
Finally of course, have the balance end up correct but subtracting the Full Principal payment.
I think i have the 1st Tab done correctly, but when i go into the table, that's where it goes wrong.
I believe i correctly changed the formula in Column F, so that it adds the additional Principal Payment, and it is adding it to the Total payment in Column I, but the balance is incorrect.
and i am not sure its deducting the Total Principal payment (including the extra) so that it refigures the Interest on the remaining balance the next month.

So Help??

	#	payment date	opening balance	interest	principal	property tax	total payments	closing balance	# remaining
	1	5/6/2020	$130,000	$339	$1,218	$549	$2,106	$128,782	115
	2	6/6/2020	$128,782	$333	$1,217	$549	$2,099	$127,565	114

Formula under principal: =IFERROR(IF(AND(ValuesEntered,[@[paymentdate]]<>""),-PPMT(InterestRate/12,1,DurationOfLoan-ROWS($C$4:C4)+1,[@[openingbalance]])+'Mortgage Calculator'!$E$9,""),0)
Formula under Total Payment: =IF([@[paymentdate]]="",0,[@interest]+[@principal]+[@[propertytax]])
Formula under Closing Balance: =IF([@[paymentdate]]="",0,[@[openingbalance]]-[@principal])

I assuming looking at that the last 2 cell are not adding in the Cell from Tab1, Morgage Calculator E9 but how do i fix that?

 

[Wheelman666]

After plying with it some more, i think i actually do have it correct. can someone check my work to make i did do this correctly?