how to have user connect remote database without any configure

A cryptic question - it would help if you provide some more detail.

If you are using ODBC, you can use a data source that resides remotely in the same way as one that resides on the local computer. In C++ program that utilizes ODBC the location of database is totally transparent.

You can configure data source programatically using something like:

SQLConfigDataSource(NULL,ODBC_ADD_DSN, "Excel Files (*.xls)",
                   "DSN=New Excel Data Source\0"
                   "Description=New Excel Data Source\0"
                   "FileType=Excel\0"
                   "DataDirectory=Q:\\EXCELDIR\0"
                   "MaxScanRows=20\0");

Where Q: could be a remote location