I'm not seeing where my title suggested another sub to the main form, sorry if it read that way to you.
The reason would be that a subform is a form that resides in a subform control that has to be on a main/parent form. So to ask if it's possible to have a tab control on a subform (Subform & Tab Control - Not sure if it is possible??) the answer is yes. However,
double click on a single line item to open the tab control form
suggested another form was to be opened, not a subform. Hence my guess. Yet you are calling that form a subform...
I have another subform that is in not on the main form and in tab-control format
and I don't understand the notion of "tab-control" format other than to guess it is a form with a tab control on it.
What you've said below is correct. My main form has a cbo box that drives results on two separate subforms on the main form . . . both subforms are query driven are in spreadsheet view, call one: sfrmContributions; call two: sfrmDeals.
So I will assume you want a double click event on a subform on the main form to open another form to display records linked to the combobox control on that main form.
First, identify the primary key of the sub form (which links it to the main form). That field should also be the primary key of the recordset for the other form you want to open. Next, because you are using datasheet (not spreadsheet) view, you will have to decide whether to enforce the user to click on a specific field, or allow any field to accept the double click event, or force user to click on the record selector (left side of record row). If record selector, you can use the subform's double click event. If only one field, you will have to indicate which and use that field/control's double click event. To allow any, you will have to use the dc event for each control of your datasheet. In the later case, rather than repeat the same code several times (a pain if you have to modify it) I would create a form level function that can be called by the double click event of ANY of the subform datasheet controls. You would simply type in the function name in the dc event to affect the function call. This function would look like
Code:
Private Function OpenDealDetails()
DoCmd.OpenForm "thirdFormName",,,"[DealDetailsID] = " & Me!DealID
End Function
where DealDetailsID is the primary key on the third form and DealID is the primary of the main form's subform, which also happens to be the primary of the main form ID. In effect, you are simply linking the third form to the subform the same way the subform is linked to the main form. You may have noticed that I omitted any reference to the combo box. The method I describe is more reliable because I do not know anything about the combo's row source. It could be a value list or have its allow edits or list additions properties set in such a way that a user can change what's displayed, then invoke the double click event. You could end up trying to load records that don't exist into the third form.
No slight intended, but I think you may benefit from boning up on terminology since many of the names you use to describe your db objects don't really exist. It would help anyone trying to help you.