Help with % Mix which then becomes recursive

Thanks for this, unfortunately it doesn't solve my issue.  I realize I didn't explain the issue properly.  Instead of a new total January value, i would like a new product spread in the original January column using a fixed value for product D. 

I have built the %s as measures already, but i almost want to do a "paste value" like we could in excel so that those percentages are locked and not recursive.  Hope my explanation makes sense.