setting public variables for peramiters in a report in micresoft access vba

I have a database in Microsoft access. There is a year to date report brought up by a form which sets the parameters for the report with public variables. This report worked in earlier an version of access but does not work with access 2007. The variables are still set in the main report but are not carried down to the sub reports. The sub reports query the database but need the variables from the main report (such as year, start month and end month) to filter the info supplied. The only way the report works now is if I type in the parameters 10 times, once for each sub report. How do I correct this problem?