Why dont you use this field as a page - maybe it would be worth to slightly changed value of the falg so your sheets would have more friendly names, but still it would work!
That automaticly will create one report with value filtered to 0 another with value filtered to 1 and create a sheet for aeach of it.
If you have more values in it you can filter whole report then to only 0&1
If Flag is a dimension with 2 values (0, 1) only, then use the Page feature:
If Flag is a dimension with many values but you only want 2 sheets (for Flag=0 and Flag=1), then:
- Build a filter for Flag =0,1 and apply this to the Report (or User or Task)
- Use the Flag dimension in the Page feature.