Converting 1 to January so you can then GROUP by quarter in PIVOT

Hi,

I have sales data where each month shows as a numerical value i.e. January is 1, Feb is 2 etc and want to firstly enter a formula to change the number value to a text value so I can then have the ability to convert to a pivot table and then group my data by quarter. I will be going back and historically filling in sales data going back 10yrs as part of a project and all the source sheets show 'periods' instead of the correct month name. I have tried =TEXT(B2*29,"mmm") but once converted to month name it will not allow me to group this in a pivot table. I can group period 1-3, 4-6 etc but I want to show the proper quarter names of the year.

I have attached an example workbook.

If anyone can I help I would appreciate it.

Thanks