Better Excel Formula for Complex Lookup - excel-2007

Question

I am trying to improve a complex lookup procedure that I have inherited. The lookup was being generated through several UDF combined with some standard worksheet functions. However, the issue was that when the user updated some data in the source sheet, the re-calc time was unacceptable.
So, I took a look and thought I may be able to write a better Excel formula only solution. Well, I did find a solution, but it is too much for Excel to handle on large data sets, and it crashes (understandably so!) when my VBA runs the formulas against the dataset.
Now, I could implement this in VBA fully, but then the user would have to press a button or something to update after every change. What I would like is a more simpler approach, if there is one, using some of the advanced Excel 2007 formulas. Since I am not as well-versed on those formulas, I am reaching out for some help!
Okay, here is what I have to work with.
SourceSheet
Tid's, Settlement Dates, and month-end prices (layer periods identified by 1,2,3, etc) in columns like below
Tid SettleDate 1 2 3 4 5 6 7 8 9 10 ... n
FormulaSheet
Amongst other columns, I have the following columns
InitLayer LiqdLayer InstrClass Tid SettleDate InitPrice LiqdPrice Position
I also have the layer numbers in columns to the right of the entire data set, like this:
1 2 3 4 5 ... n
What I need to do is fill in the proper price changes in these columns based on some logic in the dataset by looking up the prices on the source sheet.
In psuedo-formula, this is what I need to happen for each layer column in the FormulaSheet
If Layer < InitLayer OR Layer > LiqdLayer Then Return "-"
ElseIf Layer = InitLayer Then (Layered Price - InitPrice) * Position
where Layered Price is obtained by finding the Intersect of the LayerNumber
Column and Tid Row in the SourceSheet
ElseIf Layer = LiqdLayer Then Previous Layered Price * Position
where Previous Layered Price is obtained by finding the Intersect of the Previous
LayerNumber Column and Tid Row in the SourceSheet
Else (LayeredPrice - Previous Layered Price) * 6
where Layered Price and Previous Layered Price are defined as above
End If
I did come up with this formula, which works well on small data sets, but its toooooooooo big and nasty for large data sets, or just too big and nasty period!
=IF(OR(CH$3<$AT6,CH$3>$AU6),"-",IF($AT6=CH$3,(HLOOKUP(CH$3,layered_prices,RIGHT(ADDRESS(MATCH(IF($AX6="CUR",$T6 & " " & $G6,$T6),IF($AX6="CUR",layered_curtid,layered_tid),1),1,4),LEN(ADDRESS(MATCH(IF($AX6="CUR",$T6 & " " & $G6,$T6),IF($AX6="CUR",layered_curtid,layered_tid),1),1,4))-1)-1,FALSE)-$AV6)*$C6,IF($AU6=CH$3,($AW6-HLOOKUP(CG$3,layered_prices,RIGHT(ADDRESS(MATCH(IF($AX6="CUR",$T6 & " " & $G6,$T6),IF($AX6="CUR",layered_curtid,layered_tid),1),1,4),LEN(ADDRESS(MATCH(IF($AX6="CUR",$T6 & " " & $G6,$T6),IF($AX6="CUR",layered_curtid,layered_tid),1),1,4))-1)-1,FALSE))*$C6,(HLOOKUP(CH$3,layered_prices,RIGHT(ADDRESS(MATCH(IF($AX6="CUR",$T6 & " " & $G6,$T6),IF($AX6="CUR",layered_curtid,layered_tid),1),1,4),LEN(ADDRESS(MATCH(IF($AX6="CUR",$T6 & " " & $G6,$T6),IF($AX6="CUR",layered_curtid,layered_tid),1),1,4))-1)-1,FALSE)-HLOOKUP(CG$3,layered_prices,RIGHT(ADDRESS(MATCH(IF($AX6="CUR",$T6 & " " & $G6,$T6),IF($AX6="CUR",layered_curtid,layered_tid),1),1,4),LEN(ADDRESS(MATCH(IF($AX6="CUR",$T6 & " " & $G6,$T6),IF($AX6="CUR",layered_curtid,layered_tid),1),1,4))-1)-1,FALSE))*$C6)))
Formula Key
CH = Layer Number
CG = Previous Layer Number
AT = InitLayer
AU = LiqdLayer
AX = InstrClass (used to find a separate lookup for Currencies)
T = Tid
G = SettleDate (used to find a separate lookup for Currencies)
AV = InitPrice
AW = LiqPrice
C = Position
layered_prices = named range for the range of prices under the layer columns in SourceSheet
layered_tid = named range for tid rows in SourceSheet
layered_curtid = named range for currency tid rows in Source Sheet (just a separte lookup if InstrType = Currency, formula the same
Are there any other formulas, or combination of formulas that will allow me to get what I am seeking in a more efficient manner than the monstrosity I have created?

Answer 1

I agree with Kharoof's comment. You should break this formula into several columns. From my count, you need 4 more columns. The benefits are two-fold: 1) Your formula gets much shorter because you're not repeating the same function over and over and 2) You save memory because Excel will calculate it once instead of several times.
For instance, you call the exact same ADDRESS function four times. Excel doesn't "remember" what it was when evaluating a formula and so it calculates it anew each time. If you put it in it's own cell, then Excel will evaluate the cell before any cells that depend on it and store it as a value instead of the formula. When other cells reference it, Excel will provide the pre-evaluated result.
First, here's what your final formula should be: (The names in [brackets] indicate that a helper column fits there. It'll be some cell reference like CI$3 but I wasn't sure where you'd want to put it. You'll have to update those references based on where you add these columns.)
=IF(OR(CH$3<$AT6,CH$3>$AU6),"-",IF($AT6=CH$3,([LayerNumber]-$AV6)*$C6,IF($AU6=CH$3,($AW6-[PreviousLayerNumber])*$C6,([LayerNumber]-[PreviousLayerNumber])*$C6)))
And here are the four helper columns:
[ADDRESS] = ADDRESS(MATCH(IF($AX6="CUR",$T6 & " " & $G6,$T6),IF($AX6="CUR",layered_curtid,layered_tid),1),1,4)
[RIGHT] = RIGHT([ADDRESS],LEN([ADDRESS])-1)
[LayerNumber] = HLOOKUP(CH$3,layered_prices,[RIGHT]-1,FALSE)
[PreviousLayerNumber] = HLOOKUP(CG$3,layered_prices,[RIGHT]-1,FALSE)
By splitting it up, each step of the formula is easier to follow / debug as well as faster to process for Excel. If you want some quantitative improvement, the five formulas combined will be around 70% shorter than the single formula you have right now.