Values to(from) file by dataport without request form

I need to import some data (orders for instance) to Navision from file. But there is no "customer no." in this file and user has to select "customer no." himself.

Earlier, i would make request form in dataport where would give to user a textbox to select "Customer No.".

There is a very good option in dataport: select filename , and export/import option. And when i make request form it disappears.

I found a way, how to select customer for import (or export, das macht nichts) without request form:

User just set filter in dataport on field he need to feel with specified value.

OnPreDataport 
    // I save this value : 
  Variable := Record.Getfilter(Field)
   // where Variable is of Field Type. 


OnPreDataItem 
  SETFILTER(Field,'');

OnAfterImportRecord (or OnBeforeExportRecord)
   Field:= Variable;