I'm afraid I don't understand your question, but I do suggest you name fields more descriptively, rather than just A1, A2, etc.
I don't know if it is what you are looking for, but you can use the ExecuteSQL() function to retrieve meta data of your database, i.e. field names for a specific table. Read this excellent blog article: http://www.databuzz.com.au/using-executesql-to-query-the-virtual-schemasystem-tables/
Its not easy to decipher your post zhaohongbin.. all i can say is that if you have field names A1, A2, A3 in a table you need to start with database design theory and focus on data normalization and modeling. Then dive into the FileMaker training series
Yes, and there are still Design Functions that also give you metadata.
This is particularly useful if you need to know fields on a layout, for example, not just in the table or TO. Or the "bounds" of a field on a layout (where it's located).
Also take a look at this script step for setting fields contents by calculated names (and perhaps dynamically?)
Remember that changing the field (or table, or layout) names, may cause problems for any "hard-coded" values you may use in the above functions and script steps:
I may be able to decipher using plain text ciphering. He want this on B (repeated calculation field).
Evaluate ( "A" & Get(CalculationRepetitionNumber) & "" ; [ A1 ; A2 ; A3 ; A4 ] )