1. A method in a data processing apparatus for accessing cell data of a spreadsheet file cell in a record-based computer readable-medium, comprising: determining whether cell data location information for a selected spreadsheet file cell is contained in a first grid record of a plurality of grid records, each grid record storing a mapping between a plurality of spreadsheet file cells and the location of their corresponding cell data location information in a cell data record implemented in the record-based computer readable-medium; if the cell data location information is contained in the first grid record, determining the cell data location information from the first grid record; determining the location of cell data corresponding to the spreadsheet file cell in the cell data record based on the cell data location information; and extracting the cell data from the cell data record, wherein the cell data location information indicates the location of cell data in the cell data record, the cell data location information is a 16 bit matrix, and the first 10 bits of the 16 bit matrix indicate the cell data record containing the cell data, and the last 6 bits of the 16 bit matrix indicated the location of the cell data within the cell data record.