Solved!
Private Sub btnGo_Click()
DoCmd.BrowseTo ObjectType:=acBrowseToForm, _
ObjectName:="frmBrowseTestators", _
PathToSubformControl:="frmNavigation.NavigationSubform", _
WhereCondition:="ID = " & txtTID, _
Page:="", _
DataMode:=acReadOnly
End Sub
Does the trick. The lesson seems to be...