Generate rows for missing months with 0 value for sales

Can somebody help me on this? I have been reading the forum and trying to do it myself but have always failed to find the right result.

I want to create rows which would add missing months in my file, but those new months should have 0 value for both pack and cash sales. The starting point for new months would be the minimum date in Date field and the ending point would be maximum date in Date field.

As you can see in the attached file I am missing May until June 2013 data for Xantium product and March until June 2013 data for Zurat. Can we add those months with 0 value for Packs and Cash value?

Thanks a lot for helping on this one.

Gorazd