Today Or Now Functions In Queries To External Data Sources?

Is it possible to use a today or now function in an sql query to an external datasource in excel 2007? I have an excel 2007 spreadsheet, that I have linked to our financial database (MySql) using the database wizard. I can get the tables to display in excel no problem. One table shows how much staff have billed in each invoice period. I would like to create a query in excel, so that when this table displays in excel it shows how much each staff member has billed for the current invoice period, as opposed to all of them.

We weren't sure how to do this, so we decided to do a query to pull out the current invoice period, then we could combine this pivot table with the one for the amount billed table to give a table showing the amount each staff member has billed in the current invoice period (do this bit in excel).

The problem is we can't seem to make the query to pull out the current invoice period work. We have tried the query below, and all the variations of it that we can think of

SELECT invoice_period FROM tbl_invoice_periods WHERE STR_TO_DATE('" & NOW() & "', '%d/%m/%Y') BETWEEN start_date AND end_date;

We have also tried referencing a cell which shows the current date, but we cannot get this to work either (we may have made a mistake in the query here, we are not entirely sure how to reference an individual cell). The only way we have been able to get it to work is if you enter the current date directly into the query, but obviously this means it's no longer automated, which isn't a solution.