usually each connection takes some handshaking when connecting and eats up a bit of memory. The same goes for the server. It's not uncommon to have different programs each having it's own connection, but to me, it's odd to have one program with so many connections (from one sheet?). I'd expect, with so many connections being used, It'll slow down the program but can't say for sure.
Other that that, I'm not aware of a way to put a limit on a certain user's connection-count in sql-server or windows for that matter.