SOLR to pivot on date range query

[Lewin Joy (TMS)]

Hi,

I have data that is coming in everyday. I need to query the index for a time 
range and give the facet counts ordered by different months.
For this, I just have a solr date field, entryDate which captures the time.

How do I make this query? I need the results like below.

Jan-2015 (2000)
        entryType=Sales(750)
        entryType=Complaints(200)
        entryType=Feedback(450)
Feb-2015(3200)
        entryType=Sales(1000)
        entryType=Complaints(250)
        entryType=Feedback(600)
Mar-2015(2800)
        entryType=Sales(980)
        entryType=Complaints(220)
        entryType=Feedback(400)

 
I tried Range queries on 'entryDate' field to order the result facets by month. 
But, I am not able to pivot on the 'entryType' field to bring the counts of 
"sales,complaints and feedback" type record by month.

For now, I am creating another field at index time to have the value for 
"MONTH-YEAR" derived from the 'entryDate' field.
But for older records, it becomes a hassle. Is there a way I can handle this at 
query time? 
Or is there a better way to handle this situation?

Please let me know. Any thoughts / suggestions are valuable.

Thanks,
Lewin