I am new to UNIX and I need a sample awk or sed program to solve the following problem.

I have a file with the following format. The file is comma delimited. Each record has header information followed by looping detailed information. In addition the detailed information will vary based on a value found in the header information. For example if the header information has a value of 48 then the detail will have 48 sets of detail information. A set of detailed information is a set of 3 fields. The other value is 24, so the detail will either have 48 sets or 24 sets of detail.

What I want to do is replace the delimiter after the value 48 or 24 and around each triplete of information. I highligted the areas in bold where I want to change the comma to a semi colon.

Sample of current record:
MEPMD01,19970819,Sensus,SDGE,SDGE,,200705221435,1888961,OK,E,KWH,1,00000015,48,200705210715,R 00 40,2.0000,200705210730,R 00 40,1.0000,200705210745,R 00 40,2.0000,200705210800,R 00 40,1.0000,200705210815,R 00 40,2.0000,200705210830,R 00 40,2.0000,200705210845,R 00 40,1.0000,200705210900,R 00 40,2.0000,200705210915,R 00 40,2.0000,200705210930,R 00 40,1.0000,200705210945,R 00 40,2.0000,200705211000,R 00 40,1.0000,200705211015,R 00 40,2.0000,200705211030,R 00 40,2.0000,200705211045,R 00 40,1.0000,200705211100,R 00 40,2.0000,200705211115,R 00 40,2.0000,200705211130,R 00 40,1.0000,200705211145,R 00 40,2.0000,200705211200,R 00 40,1.0000,200705211215,R 00 40,2.0000,200705211230,R 00 40,2.0000,200705211245,R 00 40,1.0000,200705211300,R 00 40,2.0000,200705211315,R 00 40,2.0000,200705211330,R 00 40,1.0000,200705211345,R 00 40,2.0000,200705211400,R 00 40,1.0000,200705211415,R 00 40,1.0000,200705211430,R 00 40,2.0000,200705211445,R 00 40,1.0000,200705211500,R 00 40,1.0000,200705211515,R 00 40,1.0000,200705211530,R 00 40,1.0000,200705211545,R 00 40,1.0000,200705211600,R 00 40,1.0000,200705211615,R 00 40,1.0000,200705211630,R 00 40,1.0000,200705211645,R 00 40,1.0000,200705211700,R 00 40,1.0000,200705211715,R 00 40,1.0000,200705211730,R 00 40,1.0000,200705211745,R 00 40,1.0000,200705211800,R 00 40,1.0000,200705211815,R 00 40,1.0000,200705211830,R 00 40,1.0000,200705211845,R 00 40,1.0000,200705211900,R 00 40,1.0000

Roy Ayala