Please post a sample/dummy dataset so we can send you the formula.
Some examples in other posts:
http://forums.visokio.com/discussion/comment/9759/#Comment_9759
http://forums.visokio.com/discussion/comment/6514/#Comment_6514

Here is an example:
# Quarter Product
53 2016 Q1 Product 1
79 2016 Q1 Product 2
100 2016 Q1 Product 3
44 2016 Q2 Product 1
15 2016 Q2 Product 2
108 2016 Q2 Product 3
68 2016 Q3 Product 1
0 2016 Q3 Product 2
130 2016 Q3 Product 3

Please see file attached. Formulas are in the DataManager space, so will continue to work with the new data coming in. This being a dummy set, periods are running just Q1-Q3. If your dataset stretched over several years, you will need to add a field to dynamically rank the quarters, so you get continuous evaluation from Q4-Q1 next year, for example.
Formulas used:

%QoQ difference
IF(
[Quarter number]>1
,
(SUBSET_SUM([Value], SUBSET3([Product],[Year],[Quarter number]))
-
SUBSET_SUM([Value], SUBSET3([Product],[Year],[Quarter number],[Product],[Year],[Quarter number]-1))
)
/
SUBSET_SUM([Value], SUBSET3([Product],[Year],[Quarter number],[Product],[Year],[Quarter number]-1))
,
null)

Market share Product/Quarter
SUBSET_SUM([Value], SUBSET3([Product],[Year],[Quarter number]))
/
SUBSET_SUM([Value], SUBSET2([Year],[Quarter number]))



Thank you! The formula worked well!