There's at least a couple of ways of doing this I think but I find this method fairly straight forward...
If you launch your report from a button on a form, then add a text box to your form where the user has to put the required week number. Then each of your queries can use the value in the text box as part of the criteria for the query i.e. each query will automatically return only the required weeks to the report.
You can also use the same text box on the form to add a dynamic heading to your report. e.g. "Report for week " & Forms!myForm!myChosenWeekBox
If you are launching your report from the report list rather than from a form then you will have to run some code in the OnOpen event to grab the week number and store it somewhere e.g. in a table. Then use Dlookup in the criteria for your queries to get the week number form the table.
If you are handy with VBA then you can create your crosstab queries on the fly negating the need to store variables.
I have tried top use combo box, where are week number, but query dosn't work. Gives me error, but what gind i can't tell right now. I dosn't have the database in this computer. I will tell it tomorrow.