I don't know what you mean by "single". Anyway, on second thought, because the fields bear so little relation to each other, it might be better to start by using Table1 as your main report, with a group on Account # and with no record selection criteria. Add a subreport in a group header section that uses Table2 and limit the records to the week you are concerned with using a parameter.
Add a second subreport that uses Table 4 to the group footer (or another group header section), and suppress the detail section in the main report. In this subreport, use the record selection formula we mentioned earlier, and also create a date parameter with the same name as the one in the first subreport.
In the main report, create the same-named date parameter, and link the two subreports on the acct and on the date parameter (using the lower left dropdown box to select the parameter).
In the second subreport, try my earlier suggestion of grouping by month and then also by week, but use conditional suppression on the week groups using the date parameter (don't use it in the record selection formula), but instead use it in the suppression formula (this assumes that you are reporting data through the currentdate, otherwise you could use it in your record selection formula to delimit the end of the date range). It would help if you explained what the particular week that you are reporting on is--the most recent full week or?--so that we could determine the best type of date parameter to use.
Then the subreports should be formatted to suppress if blank, and the main report group sections should also be formatted to suppress if blank. If you put the account info (wtih table1) in your first subreport and use an equal join within the subreport between the two tables, then if there is no purchase info, the sub should suppress. Don't put any actual data in the main report other than inserting the group on account.
-LB