Double Interpolation

[hatman]

I have test data consisting of Actual Pressure and Actual RPM's... tens of thousands of lines of data in dozens of files spanning many years. I finally gained access to the table(s) that define the algorithm to calculate Volume from these two parameters. It involves a double interpolation. So I built the sheet that will calculate the volume for one set of values:

RSA Volume Caculation.xls
	C	D	E	F	G	H	I	J	K	L
2	1547.20	ActualRPM's
3	1.43	ActualPressure
4
5	32.5	InterpolatedVolume
6
7		RPM's
8		1000	1100	1200	1300	1400	1500	1600	1700	1800
9	Pressure	0.2	0.25	0.3	0.35	0.4	0.45	0.55	0.6	0.7
10		0.3	0.4	0.5	0.6	0.7	0.8	0.9	1	1.15
11		0.45	0.55	0.7	0.8	0.95	1.1	1.25	1.4	1.55
12		0.65	0.75	0.9	1.05	1.25	1.4	1.6	1.85	2.05
13		0.8	1	1.15	1.35	1.6	1.85	2.1	2.25	2.55
14		1.05	1.25	1.5	1.75	2.05	2.3	2.5	2.7	3.05
15
16	RPMInterpolation			1547.20	RPM's		PressureInterpolation
17	6	MatchColumn					3	MatchRow
18	7	MatchColumn+1		Pressure	Volume		4	MatchRow+1
19				0.4972	0
20	0.472	PercentOffset		0.8472	11.59		0.800988875	PercentOffset
21				1.1708	23.19
22				1.4944	34.78
23				1.968	46.38
24				2.3944	57.97
RSA_Volumes

Not TOO bad. But what I need to do is actually GRAPH the volume result as a function of time in my data. That means performing this interpolation thousands of times. One solution is to use VBA to populate this sheet, and caopy/paste the result back into the data table, for each line of data. Sure, I personally can do that without much difficulty. But that isn't a solution that I can easily pass on to other people who collect and interpret this data in other departments. What I REALLY want is a single formula, or even a series of formulas, that will claculate this result without the intermediate table:<SCRIPT language=JavaScript src="http://www.interq.or.jp/sun/puremis/colo/popup.js"></SCRIPT><CENTER><TABLE cellSpacing=0 cellPadding=0 align=center><TBODY><TR><TD style="BORDER-RIGHT: #000000 0.5pt solid; BORDER-TOP: #000000 0.5pt solid; BORDER-LEFT: #000000 0.5pt solid" bgColor=#0c266b colSpan=6><TABLE width="100%" align=center border=0><TBODY><TR><TD align=left><FONT color=white>Microsoft Excel - RSA Volume Caculation.xls</FONT></TD><TD style="FONT-SIZE: 9pt; COLOR: #ffffff; FONT-FAMILY: caption" align=right>___Running: 11.0 : OS = Windows XP</FONT></TD></TR></TBODY></TABLE></TD></TR><TR><TD style="BORDER-RIGHT: #000000 0.5pt solid; BORDER-LEFT: #000000 0.5pt solid; HEIGHT: 25px" bgColor=#d4d0c8 colSpan=6><TABLE width="100%" align=center border=0 VALIGN="MIDDLE"><TBODY><TR><TD style="FONT-SIZE: 10pt; COLOR: #000000; FONT-FAMILY: caption">(<U>F</U>)ile (<U>E</U>)dit (<U>V</U>)iew (<U>I</U>)nsert (<U>O</U>)ptions (<U>T</U>)ools (<U>D</U>)ata (<U>W</U>)indow (<U>H</U>)elp (<U>A</U>)bout</TD><TD vAlign=center align=right><FORM name=formCb605117><INPUT onclick='window.clipboardData.setData("Text",document.formFb202339.sltNb447362.value);' type=button value="Copy Formula" name=btCb942116></FORM></TD></TR></TBODY></TABLE></TD></TR><TR><TD style="BORDER-RIGHT: #000000 0.5pt solid; BORDER-LEFT: #000000 0.5pt solid" bgColor=white colSpan=6><TABLE border=0><TBODY><TR><FORM name=formFb202339><TD style="WIDTH: 60px" align=middle bgColor=white><SELECT onchange="document.formFb202339.txbFb150492.value = document.formFb202339.sltNb447362.value" name=sltNb447362><OPTION value="" selected>O12</OPTION></SELECT></TD><TD align=right width="3%" bgColor=#d4d0c8>=</TD><TD align=left bgColor=white><INPUT size=80 value=7331-1 name=txbFb150492></TD></FORM></TR></TBODY></TABLE></TD></TR><TR><TD style="BORDER-RIGHT: #000000 0.5pt solid; BORDER-TOP: #000000 0.5pt solid; BORDER-LEFT: #000000 0.5pt solid; BACKGROUND-COLOR: #d4d0c8" align=middle width="2%"></TD><TD style="BORDER-RIGHT: #000000 0.5pt solid; BORDER-TOP: #000000 0.5pt solid; FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: menu; BACKGROUND-COLOR: #d4d0c8" align=middle><CENTER>O</CENTER></TD><TD style="BORDER-RIGHT: #000000 0.5pt solid; BORDER-TOP: #000000 0.5pt solid; FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: menu; BACKGROUND-COLOR: #d4d0c8" align=middle><CENTER>P</CENTER></TD><TD style="BORDER-RIGHT: #000000 0.5pt solid; BORDER-TOP: #000000 0.5pt solid; FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: menu; BACKGROUND-COLOR: #d4d0c8" align=middle><CENTER>Q</CENTER></TD><TD style="BORDER-RIGHT: #000000 0.5pt solid; BORDER-TOP: #000000 0.5pt solid; FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: menu; BACKGROUND-COLOR: #d4d0c8" align=middle><CENTER>R</CENTER></TD><TD style="BORDER-RIGHT: #000000 0.5pt solid; BORDER-TOP: #000000 0.5pt solid; FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: menu; BACKGROUND-COLOR: #d4d0c8" align=middle><CENTER>S</CENTER></TD></TR><TR><TD style="BORDER-TOP: #000000 0.5pt solid; FONT-SIZE: 10pt; BORDER-LEFT: #000000 0.5pt solid; COLOR: #000000; FONT-FAMILY: menu; BACKGROUND-COLOR: #d4d0c8" align=middle width="2%"><CENTER>12</CENTER