Determines the total number of records in the grid. When this property is set to a positive value, the grid allows for exactly NUM-ROWS records. When it is set to zero (the default), the grid extends to the last record that has data defined for it. When it is set to -1, the grid extends to one record past the last record that has data defined for it. This provides a blank record at the end of the grid in which the user can add new data. In the case of 0 and -1, the grid will grow as needed when more records are added.