Passing data between DataTables

Question

Hia,
 
I'm looking to move data between two DataTables (with a twist) & am looking for some guidance......
 
I have a WinForms application that works as follows :-
 - Form_A is the main form & has graphing elements on it
 - Form_A has two DataTables (a RawDT & an AnalysisDT)
 - Form_A calls Form_B
 - Form_B is used to import data from flat files (.csv, etc.)
 - Form_B has two DataTables (an OriginalDT & a FilteredDT)
 - Form_B allows the user to select just a single column from the original flat file to import.
 
The idea behind the application is that the user can import a single column of numerical data, from a flat file. Analysis is then performed on the data, the results of which is then presented back to the user graphically.
 
I have the above working however I am struggling with passing the data from Form_B.FilteredDT to Form_A.RawDT. I've tried CopyToDataTable() without success as well as variations on :-
  frm_Main ImportTo = new frm_Main();
  ImportTo.RawDataGrid = FilteredDT; 

Any suggestions / pointers would be most helpful.
 
Thanks all.