Working with named ranges in UDFs

[JenniferMurphy]

I would like to to do some fairly complicated calculations in a UDF. And I would like to do them using named ranges, if possible.

Here's a sample table. The input data is in Columns D, E, & F. These columns have been assigned the names T, A, & B. Column G contains the calculated result. The formulas in Column G are shown in Column H. Each result in G is calculated from the data in the 2x3 range of cells in Columns D, E, & F and the current row plus the previous row. For example, the data in G4 is calculated from the data in cells D4:F5. For the last row, the "previous" row is the top row, so the value in G8 is calculated from the data in cells D8:F8 & D4:F4.

R/C	C	D	E	F	G	H	I	J
3	#	T	A	B	X	Formula in Col G	UDF	Original Equation
4	5	82.42	20	3	3.52	=(D4*F5-D5*F4)/(E4*F5-E5*F4)	=MyUDF(T,A,B)	=(T4*B5 - T5*B4)/(A4*B5 - A5*B4)
5	4	33.09	6	3	0.99	=(D5*F6-D6*F5)/(E5*F6-E6*F5)	=MyUDF(T,A,B)	=(T5*B6 - T6*B5)/(A5*B6 - A6*B5)
6	3	35.07	8	3	3.77	=(D6*F7-D7*F6)/(E6*F7-E7*F6)	=MyUDF(T,A,B)	=(T6*B7 - T7*B6)/(A6*B7 - A7*B6)
7	2	27.54	6	3	3.65	=(D7*F8-D8*F7)/(E7*F8-E8*F7)	=MyUDF(T,A,B)	=(T7*B8 - T8*B7)/(A7*B8 - A8*B2)
8	1	16.61	3	3	3.87	=(D8*F4-D4*F8)/(E8*F4-E4*F8)	=MyUDF(T,A,B)	=(T8*B4 - T4*B8)/(A8*B4 - A4*B8)

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Column I shows the UDF call I would like to be able to make. Column J shows the original equation that I am trying to implement. I would like the code in the UDF to look as much like that equation as possible.

If I could make the code in the sheet look like that equation, I probably wouldn't need the UDF.

Note that the results are added from the bottom up. New results are added at the top.

Thanks for any help...