I can think of two solutions; one is creating a calculated field returning only the Total GST Value, something like:
IF [GST Payment Type] = 'Total GST' then [Amount] end
Another option is creating similar lookup filter to only filter the view. This is a good explanation of this technique.
I attach sample workbook with the first solution.
Filter Required.twbx 134.6 KB
Using your methodology I have tried something else. The user will only be able to select the Payment type filter, therefore I have created something like:
IF [Payment Type] = 'GST/BAS' AND [GST Payment Type]= "Total GST" then [Amount]
The calculation is valid but not quite providing me on the the Total GST amount (still includes GST 1, 2 etc.)
Thanks for the suggestion Shinichiro.
Although it doesn't solve how it interacts with my dashboard, your suggestion has triggered some thought. I have been able to use Exclude in my filters and get the answer I want. Easy as that.
Eventually an easy answer to question I had. Argh!!