Toggles highlight of editable fields in Excel

h3. Purpose

This add-in allows a user to declare a cell as editable or uneditable and to toggle the cell color of editable cells. The goal is to avoid two common methods of dealing with variables in Excel sheets: setting all relevant variables to the side of the print area and referencing them with a formula (which can make sheets bulky and adds pointless formulas), and making all variables the intended print color (which is just confusing).

Instead, this add-in reserves two color indexes (1 and 23 by default). By default, Excel sets 1 to black, which is also the automatic color. 23 is a light blue. Thus, uneditable cells can be given any other color index, and editable cells can be toggled between light blue and black. As the automatic color is also black, there should be no difference in the display of editable and uneditable cells when highlight mode is off.

h3. Usage

This add-in adds a toolbar called Highlighter to all Excel workbooks. You can click "Mark as editable/uneditable" to change whether a cell will change color when highlight mode is on. "Highlight/unhighlight" then toggles that highlight mode.

Note that for some worksheets (particularly Excel 2007+), you may need to run "Prepare sheet" first, which will set all cells to the automatic color. This will overwrite any existing font color information for the current sheet, although it leaves other formatting unaffected.