Custom Excel formatting is a neat way of accomplishing rather fancy representations of values.
A custom format can have of up to 4 sections (this is from the Excel help file):
Image:Connecting the Dots
So, if you want to put something in a cell, but want it to be invisible, use ;;; (this is 3 semicolons in a row).

I format I sometime use is the following:
This gives the following result:
Image:Connecting the Dots
No matter how wide the column, the dots keep repeating !
The * in the format tells Excel to repeat the following character (the dot in this case).

Category:  Microsoft Excel  | TechnoratiTechnorati: ,