Return Value of Searched Item In Combination With IF

[PostIt]

Date	Company Name	Method	Cash	Check	CC	Wire	Invoice#	Invoice Total	Amount Paid	Still Due
03/08/16	MONA	cc			$500		45230	$500	$500	$-
03/08/16	CRANBERRY	cash	$1000				45231	$1000	$1000	$-

<tbody>
</tbody>

This is the Checks Sheet

Invoice Date	Invoice #	Customer	Due Date	Amount Due	Paid Date	Total Paid	Method	Credit Amount	CMR	Type of Credit
03/08/16	45230	MONA		$500	03/08/16	$250	cc	$250	CMR	6789
03/08/16	45231	CRANBERRY		$1000	03/08/16	$1000	cc

<tbody>
</tbody>

This is the Invoices Sheet

Windows 10
Microsoft Office Home and Student 2010
Excel Version 14.0.7 (32-bit)


I have 3 sheets.
Invoices (Paid and unpaid invoices)
Customers (All customer data)
Checks (Received payment)

Date:

=IFERROR(INDEX(Invoices,MATCH(I24,Invoices[Invoice '#],0),6),"")

Company Name:

=IFERROR(INDEX(Invoices,MATCH(I24,Invoices[Invoice '#],0),3),"")

Invoice Total:

=IFERROR(INDEX(Invoices,MATCH(I24,Invoices[Invoice '#],0),5),"")

Amount Paid:

=SUMIF(Checks[@[Cash]:[Wire]], ">0",Checks[@[Cash]:[Wire]])

CC:

=(IF(ISNUMBER(SEARCH("cc",D24)),[@[Invoice Total]],))

Still Due:

=IF(C32=""," - ",IF(OR($C$3="All Customers",$C$3=C32),[@[Invoice Total]]-[@Cash]-[@Check]-[@CC]-[@Wire]," --- "))

The issue I'm having is that generally, CC charges are paid in full.
The rare occasions that they are partially paid for or there's been a credit issued, I would like for the CC formula to be able to take the cc amount and subtract the credit amount by looking up the Invoice # and searching across that row until it comes to the credit amount.
Which would in turn be =(IF(ISNUMBER(SEARCH("cc",D24)),[@[Invoice Total]],))-(Return Search Value).

Any help would be appreciated.
Thank you!