Hi Pragati,
According to your description, you create a subscription, you only want to send emails when the negative values in your report.
In your scenario, after creating the subscription, you could query the ReportServer database to find the corresponding job like below:
SELECT
c.Name AS ReportName,
c.Path AS Report_Path,
rs.ScheduleID AS JOB_NAME
, s.[Description]
, s.LastStatus
, s.LastRunTime
,c.CreationDate
,c.ModifiedDate
FROM
ReportServer..[Catalog] c
JOIN ReportServer..Subscriptions s ON c.ItemID = s.Report_OID
JOIN ReportServer..ReportSchedule rs ON c.ItemID = rs.ReportID
AND rs.SubscriptionID = s.SubscriptionID
Then you can edit the job steps, change the Type as SQL Server Analysis Services Command. Then type the condition you preferred in Command box to fire the job. Your requirement can be achieved by following this similar concept:
Don't send that empty SSRS report.
If you have any question, please feel free to ask.
Best regards,
Qiuyun Yu