Awk program for calculating dates.

Hi All,
I have a txt file which has hundreds of lines and 41 fields. I have a requirement to pick up field 14 from the text file which is a date fiels in the following format.

Field 14 :
Data Type : NUMERIC DATE (YYYYMMDD)
Field Length : 8
Example of Data :20090415

Field 42 :
Data Type : NUMERIC DATE (YYYYMMDD)
Field Length : 8
Example of Data :20090715

I need to add 3 months to the date and add a new field as field 42 in the txt file.

This needs to be done for every line and there is no delimiter in the text file.

Any ideas would be appreciated.

What have you done so far?

The problem is I am new to awk. I know this can be done in the shell script, but there is already a awk script which does other things to the datafile.