Changing source workbook names directly in formulas

Hi All,
Need to create Working order (in Excel 2007) for filling machine in my factory. Working order is changeable from day to day and the deference is product quantity. Product quantity in working order [File - Working order] is changing according to the each sales plan [7-Jan-13.xlsx, 8-Jan-13.xlsx, 9-Jan-13.xlsx...] . File Working order is linked to the appropriate sales plan, in this case – [7-Jan-13.xlsx].
All source workbooks [sales plan 7-Jan-13.xlsx, 8-Jan-13.xlsx, 9-Jan-13.xlsx...] are at the same location in the same folder, only difference is the source workbook names.
So, is it possible to create macro for changing source workbook names directly in formulas (File - Working order – green cells), and avoid annoying browsing?
PS There are four other links in my original application witch I won’t to change with same macro...