Todo

Methods summary
PHPExcel_Calculation_Database	`DCOUNT()`	The field argument is optional. If field is omitted, DCOUNT counts all records in the database that match the criteria.
PHPExcel_Calculation_Database	`DCOUNTA()`	The field argument is optional. If field is omitted, DCOUNTA counts all records in the database that match the criteria.
PHPExcel_Calculation_LookupRef	`INDIRECT()`	Support for the optional a1 parameter introduced in Excel 2010
PHPExcel_Calculation_Statistical	`BINOMDIST()`	Cumulative distribution function
PHPExcel_Calculation_Statistical	`CRITBINOM()`	Warning. This implementation differs from the algorithm detailed on the MS web site in that $CumPGuessMinus1 = $CumPGuess - 1 rather than $CumPGuess - $PGuess This eliminates a potential endless loop error, but may have an adverse affect on the accuracy of the function (although all my tests have so far returned correct results).
PHPExcel_Calculation_Statistical	`LOGINV()`	Try implementing P J Acklam's refinement algorithm for greater accuracy if I can get my head round the mathematics (as described at) http://home.online.no/~pjacklam/notes/invnorm/