I am not sure what cells you are referring to. Assuming that you want to change the date table cells in the monthly calendar then those cells can be changed by modifying the "DayStyle" parameter in the calendar control.

By looking at EventMonth.ascx I see that the DayStyle parameter is tied to the CSS class "EventDay".

Here is the first thing I would try. Open up the module.css file and find the EventDay style area then add "height" and "width" entries. Like this:

.EventDay, .EventDay td
{
    font-size: 7pt;
    color: #0000ff !important;
    font-family: Verdana;
    width: 400px;
    height: 400px;
}

Questions and comments welcome.