ESQLC and date/datetime routines.

I'm having what would seem to be a common problem so if anyone has a function that does this some help would be greatly appreciated. I have a datetime = CURRENT I have a date = TODAY I want to know what is the date of the day 30 business days in the future. The problem is if I use the date to add in a for loop I can exclude weekends with rdayofweek() but I can't add an interval to a date. If I use the datetime in a for loop there is no rdayofweek() type function for datetimes so there is not way to exclude weekends as non-business days. Not only that there is no way to convert between datetimes and dates! I wrote this function in 4gl months ago, but the application I am working on now is in ESQL/C. I find it hard to believe Informix would include the necessary functionality for 4gl but exclude it from ESQL/C since 4gl is really just high level C. Any ideas...Jonathan??