I left this using the openargs, but it was limited to only one field, today I decided to try something else and finally solved the main requirement of this thread, this is the code to make one textbox be filled from diferent sources depending on which form is loaded:

Code:
If CurrentProject.AllForms("frm30UserData").IsLoaded Then
Me.txtStation = Forms!frm30UserData.lstStation
Else
Me.txtStation = Forms!frm20MainStatus.cmbStation
End If
Regards!