Monitor stored procedure statistics with extended events
Your options are a bit limited in SQL Server 2008 R2 and Extended Events.  You could try rpc_completed but remember it will only register for remote procedure calls.  Here's some sample code tested in SQL 2008 R2 which shows how to create a session then read it.  Work through it, make sure you understand it and try it out:
-- xe_rpc_completed
IF EXISTS ( SELECT * from sys.server_event_sessions WHERE name = 'xe_rpc_completed' )
DROP EVENT SESSION [xe_rpc_completed] ON SERVER
GO

-- rpc_completed
CREATE EVENT SESSION [xe_rpc_completed] ON SERVER 
ADD EVENT sqlserver.rpc_completed
    (
    ACTION ( package0.callstack, sqlserver.session_id, sqlserver.sql_text, sqlserver.tsql_stack )
    )
ADD TARGET package0.asynchronous_file_target (
     SET filename = 'd:\temp\xe_rpc_completed.etl', metadatafile = 'd:\temp\xe_rpc_completed.mta' )
WITH ( MAX_MEMORY = 4096 KB, EVENT_RETENTION_MODE = ALLOW_SINGLE_EVENT_LOSS, MAX_DISPATCH_LATENCY = 30 SECONDS, MAX_EVENT_SIZE = 0 KB, MEMORY_PARTITION_MODE = NONE, TRACK_CAUSALITY =OFF, STARTUP_STATE = OFF )
GO


-- Start the session, collect some data
ALTER EVENT SESSION [xe_rpc_completed]
ON SERVER
STATE = START;
GO
    

IF OBJECT_ID('tempdb..#tmp') IS NOT NULL drop table #tmp

SELECT IDENTITY(INT,1,1) rowId, object_name, CAST( event_data AS XML ) event_data
INTO #tmp
FROM sys.fn_xe_file_target_read_file('d:\temp\xe_rpc_completed*etl', 'd:\temp\xe_rpc_completed*mta', NULL, NULL )
GO


-- Optionally add primary XML index; 
--!!NB this will cause table to grow up to 5x!
ALTER TABLE #tmp ADD CONSTRAINT pk_tmp PRIMARY KEY (rowId)
GO
CREATE PRIMARY XML INDEX xmlidx_event_data ON #tmp ( event_data )
GO


SELECT 
    e.c.value('@timestamp', 'DATETIME2') [timestamp],
    e.c.value('(data[@name = &quot;cpu&quot;]/value/text())[1]', 'INT') cpu,
    e.c.value('(data[@name = &quot;duration&quot;]/value/text())[1]', 'INT') duration_s,
    e.c.value('(data[@name = &quot;reads&quot;]/value/text())[1]', 'INT') reads,
    e.c.value('(data[@name = &quot;writes&quot;]/value/text())[1]', 'INT') writes,
    e.c.query('(action[@name = &quot;sql_text&quot;]/value/text())[1]') sql_text,
    e.c.query('.') event_data

FROM #tmp t
    CROSS APPLY t.event_data.nodes('event') e(c)
ORDER BY [timestamp]
GO

-- Collect some data
-- ...

-- When you're ready stop the session
ALTER EVENT SESSION [xe_rpc_completed]
ON SERVER
STATE = STOP;
GO

synchronous_event_counter probably won't help you as you just get an event and a count.  It's good for say, counting logins or deadlocks in a day, something like that.
ring_buffer probably won't help you because it's a circular area with only limited space allowed.  Basically it could run out of room and cycle over.
HTH