This covers Excel 2003, which is what I have. it may be similarly applicable to Excel 2007, which has a different menu structure. (your menu structure may be different/your mileage may vary a small bit).

Date+time/date/time

date and time is stored as a serial number. the integer part is the day number with the year starting at 1900 (but I am unsure of the equation, it is not a julian day) and the fractional part is the time broken up as hour/24 and minute/(24*60). it is actually more detailed than that, see my date calculations page.

There are a wide range of date types and time types to choose from.

colors

I have not found a way to change the colors by changing the formula. sorry. That would be really cool.

Currency

if you dislike the - sign or just prefer your negative numbers to be more pronounced, numbers such as $(12.45) are negative. You can choose this format if you so desire. The currency format automatically does this for you.

The Toolbar

• the little globe with the link makes web hyperlinks. hyperlinks appear blue and you can click on them, and they will pull up Internet Explorer.
• the greek mathematical symbol for summation sums up areas or columns or rows of numbers. it is a drop-down list of functions you can do, such as min, max, average, count, or you can pick a different function.
• the AZ does data sorting.
• Arial is a font. you can choose a font from there. it is a drop-down list.
• 10 is a font size. you can choose font sizes from there. it is a drop-down list.
• the bold B makes the cell bold.
• the italics I makes the cell italics.
• the underlined U makes the cell underlined.
• the next 3 buttons, in order, are left justify, center justify, and right justify.
• The next funny looking "a" button with the arrows is merge-and-center.
• the $ button is format currency.
• the % button formats the number as a percentage.
• the next 2 buttons, in order, increase the number of decimal points, and decreade the number of decimal points.
• the next 2 buttons, in order, decrease indent, and increase indent.
• the boxy matrix-looking button with lines that can drop down formats the lines around the cells. you can get no lines, single, thick, or double-lines, etc.
• the paint bucket lets you pick a background fill color. it is like using a highlighter pen.
• the A with the color underneath chooses the font color. that is the color of the text itself. this is different than the background color. in this case, we have red text on a yellow-filled background.