Filtering Sub Forms?

I would like to be able to apply more than one filter to a subform. It seems no matter how I try I can only have one filter affecting the records in my subform. I have had zero luck getting the child / master link on the form to return a satisfactory result in the subform as soon as i try to apply a second master / child filter. It seems the filters I'm trying to apply aren't 'stacking' and I seem to be getting either one or the other judging from the reports that are being listed in my sub form.

My data table consists of a few details concerning offices. Namely what Region the office is in, how many staff at particular grades, the office location / address contact details, and wether or not they reside in a 'strategic zone'. I've used check boxes on my data table to indicate wether an office is inside a strategic zone or outside a strategic zone.

My combo box is currently working great, it filters out all the records and only shows the offices that match the value in the 'Region' field in the subform. I just can't figure out how to get additional filters to work at the same time.

Ideally I would like to have the combo box which is working great, then a couple more conditions that the user can select to apply additional filter, especially the 'inside strategic zone' check box and the 'outside strategic zone' check box. I would also dearly like to have another combo box that will let users select 'Clusters' that an office may belong to and filter out those records that don't match.

I can use the right click on a field in my form and 'apply filter by selection' and of course that works great! Filtering all the way down until I'm left with a very short list that matches the same value of many filtered fields I've right clicked upon. But ewwww...that is not what anyone wants to have to rely on to give them data on the screen that conforms with the filter criteria they wish to apply.

Secondly, (sorry almost done!) how can I show the number of records that have a particular Yes/No check box ticked. Was thinking along the lines of having a couple of text boxes that count all the 'inside strategic zone' check boxes that are ticked and the same for 'outside strategic zone' How can I do this?

As I'm sure you will have picked up on, I am just setting out on my Access Database Learning curve, I have very limited experience but I am hoping to develop my own skills over the next few years. I have been humbled by the knowledge of the patrons here and warmed by the goodwill shown to helping the novices like myself who come here asking for your assistance.

Thanks for reading and cheers to you all.