Instinet and Harborside+ separately announced plans to expand their respective block trading services to provide institutional investors greater opportunity to reduce market impact when buying or selling large amounts of stock. Instinet will launch its Intra-Day Cross, or IDX, on Wednesday, according to a company news release. The new service allows institutions to cross trade large blocks of stock electronically and anonymously with other institutions three times a day — morning, midday and afternoon. Separately, Harborside+, in a deal with Thomson Financial, now accepts indications of interest from users of Thomson AutoEx, an online real-time network for block order indications, according to a Harborside+ news release. Harborside+ matches indications of interest electronically but handles executions manually.