Crystal Report excel percentile function

Crystal reports calculates percentiles and quartiles using the formula p*100 / n+1. For my project, I need a DLL to import into Crystal that has the excel percentile calculation of p*(n-1) +1. Function must be availabe from the 'additional function' list of crystal. If possible, I would like the function availabe from the drop down list box for summary functions. I need his code in VB6, if possible! The function must be able to calculate multiple percentiles in one pass i.e. Upper Decile, Upper Quartile, Lower Quartile etc. Function will be placed in a group footer. Calculations must cover numerous groups and cover different input columns.i.e Basic Total Additions Upper Decile 23500 25600 4500 Upper quartile 22500 23900 1258 Lower Quartile 21520 22100 980 Lower Decile 19520 20152 500 An option to calculate the values including or excluding zero values must also be available for each field. A class must be provided with no limits (realistic) to the amount of times the function can be called. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Installation package that will install the software (in ready-to-run condition) on the platform(s) specified in this bid request. 3) Complete ownership and distribution copyrights to all work purchased. ## Platform Windows 2000 professional, with crystal reports 8.5 , 9.