Reb Moishe Shternbuch -Sheva Brochos In The three Weeks

Harav Moishe Sternbuch Shlita writes*, "Even though there is no

Chiyuv to make Sheva Brochos every day but if you do make
Sheva Brochos, you are performing a Mitzvah Kiyumis.

For this reason we may make Sheva Brochos in the three weeks.
Simchas Chosson V'Kallah is a Mitzvah. Refraining from Simcha in

the three weeks is only a Minhag. The Minhag applies only to Simcha

of Reshus and not Simcha Shel Mitzvah"**. 

R. M. S. continues that the Steipler zt"l held, being there is no Mekor  for

dancing at a Sheva Brochos, therefore you should refrain from dancing

during the three weeks.

He concludes, even on Shabbos it might be advisable not to dance

especially according to those who hold not to make a Shehechiyonu

on Shabbos.(in the 3 weeks)

                 

  *  תשובות והנהגות ח" ס' קסז

He explains why this doesn't apply to weddings .**