Need Help!!! Slicer element formatting

Hi All,

I have a date format in my report from which i have extraced month to use as a slicer. i have made a calculated column from that extracted month column like below-:

=(if [Report Month]=1 then "January" else
if [Report Month]=2 then "February" else
if [Report Month]=3 then "March" else
if [Report Month]=4 then "April" else
if [Report Month]=5 then "May" else
if [Report Month]=6 then "June" else
if [Report Month]=7 then "July" else
if [Report Month]=8 then "August" else
if [Report Month]=9 then "September" else
if [Report Month]=10 then "October" else
if [Report Month]=11 then "November" else
"December")

but the slicer is displaying month names like this-:

Can anyone tell how we can dispplay month names as calender type like 

Jan

Feb

Mar

April....

and not in alphabetical order?

Regards,

Droid