Is it possible to change the style of dhxCalendarA or dhxCalendar?
If you mean the skin of calendar , it is hardcoded and can be changed by modification in
dhtmlxgrid_excell_dhxcalendar.js
line 18
this.grid._grid_calendarA.setSkin(“yahoolike”);
line 121
this.grid._grid_calendarA.setSkin(“yahoolike”);
Skin value can be changed to any one supported by dhtmlxCalendar.
Also , it possible to adjust necessary styles in dhtmlxcalendar.css if no one of existing skins suits in your case.