Add dynamic lookup to dialogfield.

Hello.

For AX 2009.

I want to add lookup to dialogfield (built on a class).

The lookup is dynamics and should related to some fields on the dynamic dialog I create.

class MyClass extends RunBase
{
    DialogField             myDialogField1;
    DialogField             myDialogField2;
    DialogField             myDialogField3;
}

protected Object dialog()
{
    Dialog dialog;
    DialogTabPage tabParameters;
    ;
    dialog = super();

    tabParameters      = dialog.addTabPage("File");
    myDialogField1     = dialog.addField(typeid(Name), "Field 1");
    myDialogField2     = dialog.addField(typeid(Name), "Field 2");
    myDialogField3     = dialog.addField(typeid(Name), "Field 3");
}

   I want to add lookup on myDialogField3, but the lookup is dynamics, and related to the values that on field1+field2

i.e  myDialogField3 shows currencies, and the currencies are limits to specific currencies according to myDialogField1   + myDialogField2.

Thanks :)