Another seminar is planned for June, ents and sponsors.lion.Frost Bank Plans GroundbreakingC7Colorful groundbreaking ceremonies for the new $20 million downtown Frost National Bank building'on West Houston Street between Main Avenue and North Flores Street are scheduled at 4 p.m. Tuesday.A total of 10:1 balloons, representing the bank’s years of service to the community, will surround the construction site, flying at about 300 feet to illustrate the height of the 20-story skyscraper.Tom Frost Jr., board chairman, will give the principal address, after whichDon Garrett, president, will sign the construction contract with contractor Henry C. Beck.(’. Linden Sledge, vice chairman of the board, will leave the speakers platform to start work of drilling crews, marking official beginning of construction.A helicopter will approach from the adjoining Frost Motor Bank roof and hover over the site, at the level balloons are flying, while the balloons are released to climax the ceremony.•*Refreshments will le served at 3:30 p.m. before the ceremony begins.On the speakers platform with bank officials will be representatives of Charles Luck man Associates of New York, p rinciple architects; Bartlett, Cocke Associates of San Antonio, associate a r c h i t e c t s; and Cushman and Wakefield of New York, project consultants.The building is expected to be completed in 1973.