Reports :: Filtering Subreports On Main Report

I have a database (Access 2007) that handles a large number of consultants. Each consultant has a number of skills, has worked in a number of countries, and speak several languages. As contracts come in, I wish to generate a report based on the skill set, language and country/countries that best suits the contract; thereby identifying a group of most suitable consultants. I have designed a report with three sub reports for skills, languages and countries. Each sub report is linked to the main report through Link Master/Child fields using the ConsultantID. That's all fine; I get a report showing all consultants listing all their qualities.

Now, I want to be able to filter the sub reports on the three aspects: Skills; Countries; and Languages.

In the past, for other applications, and with the unfiltered form in preview I have used a popup form with unbound Combo Boxes to generate a string to use in the reports filter. I think I got that technique from Allen Browne, and it has really served me well.

Now, however, I can't use this technique since I can't set the filter for the sub reports. I thought that I might be able to use the Link Master Field with text boxes on the main report, but haven't managed to figure that out.