Modules & VBA :: Add WHERE Clause To Query (queryDef)

I have a TRANSFORMED query:

Code:
TRANSFORM nz(count(T_qa.qaQAPK),0) AS SumOfQAs
SELECT month(qaDate) AS QAmonth, Count(T_qa.qaQAPK) AS QAs
FROM Q_ALL_qa
GROUP BY Month(qaDate)
PIVOT month([qaDate])
IN (1,2,3,4,5,6,7,8,9,10,11,12);

This query is record source for a report, then this report show all calculations in a form.

I have 7 of each (query + report) all showing on the same form.

All those queries calculate data for all departments.

In the form, I have placed a combobox.

What I want is to create a vba code which will add clause WHERE to all queries at the same time and then run it.

Code:
WHERE qaDeptFK=Forms!F_CompLvl.cboDeptStats

However, if nothing has been selected in the combo, I want the queries to calculate data as normal, for all departments.

Where do I place the vba statement? Is it under combobox AfterUpdate event?

I am planning to use this: (As I never done it before)
[URL] ....
Modifying SQL On-The-Fly section