how to find difference between two "stats count" used in two different saved search

[snabi]

So i have two saved search queries
1. sourcetype="x" "attempted" source="y" | stats count
2. sourcetype="x" "Failed" source="y" | stats count

i need to create a search query which will calculate

Passed item = (sourcetype="x" "attempted" source="y" | stats count) - (sourcetype="x" "Failed" source="y" | stats count)

and display Passed item count by hours

[sideview]

sourcetype="x" source="y" (attempted OR failed) | eval isAttempted=if(searchmatch("attempted"),1,0) | eval isFailed=if(searchmatch("failed"),1,0) | stats sum(isAttempted) as attempts sum(isFailed) as failures | eval successes=attempts-failures

However I would examine the matching events for the "attempted" and "failed" searches very carefully to maked sure there aren't any false positives or negatives. Possibly this is already a boiled-down example. Note that you can have very complex boolean logic in the (attempted OR failed) side, and you can have the correspondingly complex boolean logic embedded into the searchmatch() functions so you'll be fine even if your actual case is more complex.

UPDATE:

If using eval syntax right in the stats command is more your style, that can be done too and it becomes a lot more compact:

sourcetype="x" source="y" (attempted OR failed) | stats count(eval(searchmatch("attempted"))) as attempts count(eval(searchmatch("failed"))) as failures | eval successes=attempts-failures

[lukejadamec]

It looks like you're trying to subtract apples from oranges, which cannot even be done on paper let alone splunk.
If you're trying to remove a subset of a set and the remaining items by hours, then you don't want to use stat counts. Just use a search that excludes them like this:
sourcetype="x" source="y" "attempted" | search NOT (sourcetype="x" source="y" "Failed") | stats count by _time,passeditem