I am working on a spreadsheet which contains a number of reference data sheets (named “Reference data 2009”, “Reference data 2010” etc). As their names suggest, these sheets contain reference data applicable to the particular year. This reference data is used to perform various calculations in a “Calculations” sheet.
On the “Calculations” sheet, the user specifies the year for which they wish to perform calculations. At present, I am using the volatile INDIRECT function to perform various HLOOKUP calculations along the following lines:

=IF(D15>=HLOOKUP('Detailed net pay calculations'!D16, INDIRECT("'Reference data" & 'Detailed method'!$C$2 & 'Detailed net pay calculations'!D1 & "'!$B$43:$Y$52"), 4, FALSE), “Do something”, “Do something else”)


The reason I'm using the INDIRECT function is to identify the sheet with the appropriate year (hence "Reference data"&'Detailed method'!$C$2&'Detailed net pay calculations'!D1 which could be interpreted by Excel as "'Reference data 2009NEW" or "'Reference data 2010", depending on whether there's text in cell D1).

My query
The function I'm using is working perfectly fine but I am wondering if it is possible to replace the INDIRECT function (in red) with INDEX or another non-volatile function in order to reduce the performance impact (I have a fairly large number of these types of functions).

If required, I can post a stripped down version my spreadsheet.

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Excel 2003 user (and starting to warm to Excel 2007)