Build Automated Program to Calculate Percentiles

I have comma delimited files (.txt) that have 3 fields: (field and format) Id - A6 HCPCS - A5 Charge - N I want a simple program that takes this input file, always named [login to view URL] and creates a comma delimited output file called [login to view URL] with 1 additional field, for a total of 4 fields: (field and format) Id - A6 Percentile - A6 HCPCS - A5 Charge - N The calculated percentile field will be based on the charge field. For now, the program, just needs to calculate 3 levels that will be placed as text (A5) in the Percentile field: 25th Median 75th Later, I will probably ask that the program be adapted to calculated different percentiles, such as 80% percentile, 90th percentile, etc. I need a very quick turnaround time. I am attaching a sample Input file, with multiple Id and HCPCS variations. Please calculate the percentiles for just 1 unique Id and all associated HCPCS so I can check your work. The full program will calculate percentiles for all Ids and HCPCS included in the [login to view URL] file. The check file you submit to me should be called output.txt.