First, save the record on your form... if it's not saved then the table query will show the previous value(s).
From your subform:
DoCmd.DoMenuItem acFormBar, acRecordsMenu, acSaveRecord, , acMenuVer70
'Note: Could also try me.recordset.update instead of above but found it doesn't always work consistently right
Forms("FormName").refresh 'Refreshes the form named
Forms("FormName").My_Combo.Requery 'Requeries for combo box content on the form named