Why not just publish this as two separate workbooks? I know it will add some extra effort to your publishing process, but if it were me I'd just publish twice. Once for the full workbook, a second time just for the first sheet by using the 'Sheets' selector in the publish dialog.
Then you can set your permissions for each workbook
You can use the Hybrid approach, which is the modified version of using user filters.
Create the calculated field.
Tab 2: Username( ) = [Field] //In your data which is the field having username i.e [Field]
then choose true
Tab 1: No need to create any calculated field, since it must be available to everyone.
Hi Tom -
I thought about this, but I think having two separate URL links for the different dashboards would be difficult to maintain.
Ie. I would have to distribute one URL link to certain users and another URL to the restricted group. Right now everyone is using the same link (there are a lot of people) so ideally they could continue using the current link without needing to create two.
Let me know if I am thinking about this correctly / this is what you had in mind.
That's effectively what I had in mind. I think your best solution is going to be whatever you think is easier out of that and one of the other approaches mentioned like manually maintaining a calculation in the report to exclude certain users.