How to create dynamic parser?

I want to create something called dynamic parser.

My project input is some data file like XML, Excel, CSVand ... file and I must parse it and extract its records and its fields and finally save it to SQL Server database.

My problem is that fields of the record is dynamic and I can not write parser in development time. I must provide parser in run-time. By dynamic I mean a user select each record fields using a Web UI. So, I know the numbers of fields in each record in run-time and some information about each field like its name and so on.

I discussed this type of project in question titled 'Design Pattern for Custom Fields in Relational Database'.

I also looked at Parser Generator but i did not get enought information about it and I don't know it is really related to my problem or not.

Is there any design pattern for this type of problem?