See also
http://access.mvps.org/access/forms/frm0031.htm
referencing CONTROLS on subform:
[Forms]![Main form name]![subform control name].[Form]![control name on subform]
e.g.
[Forms]![frmNP]![subNPfrm].[Form]![txtNPno]
frmNP is main form name
subNPfrm is name of subform
control on frmNP
txtNPno is the textbox control name
referencing subform PROPERTY (e.g. recordset property such as Recordcount) using object collections syntax:
Forms("MainFormName").Controls("subformControlName ").Form.Recordset.Recordcount
e.g. Forms("frmWhoUsesVendor").Controls("subWhoUsesVend or").Form.Recordsource
NOTE: again, subformControlName IS NOT THE SUBFORM NAME
Forms("frmTempDetl").Controls("frmTimeDtlSub").For m.Dirty
NAVIGATION FORMS
[Forms]![NavigationForm]![NavigationSubform].[Form]![controlName]