There is not a function per se, but there are many ways to modify or alter field values. It will help if you offer some context to what you are trying to accomplish, what your data looks like, and what it is you want to do.
For example, you may want to load to a Temp_Table, then do another subsequent load Resident and as part of that load, replace values based on script logic (or even using peek() to examine field values as you go).
Offer more details and I will be happy to help.
