Q:

Best way to represent format for presentation of cells in a grid? 

I am building a dynamic reporting feature for a client.  They want to create new stored procedures, and have them correspond to new reports.  We are using T-SQL and each cell in a grid/report can have its own formatting and/or functionality. 
I'm looking for a format specification to identify presentation, color and conditionals for data... for instance, I am thinking of something like this:
{data}|{format}
123.56|$#,##0.00
Results in ... $123.56
I am looking for standard ways to represent the formatting field, with the potential for colors and conditionals.  Is there some standard out there already? 

A:

It all depends on what you're looking for.  You have to ask yourself what types of formatting you wish to apply.  Here's some cases you might want to consider:

In-line formatting
Do you want to have a cell that contains mixed formatting (e.g. "1234.567" shows bold, regular and italic in a single cell)? 
Multi-column based output
Do you want to output a value in a cell that's based on multiple cells? 
Cell1="1234"
Cell2="56"
Cell3={Cell1}.{Cell2} 
---> which would output "1234.56"

If don't need either of those things, then all you want to do is provide a single format for the entire cell.  Let's divide it into the two formatting elements: transformations and visual effects:

Formatting "1234.5678" into "1234.56" is a transformation.  It has to be done by code that knows how to interpret the value as a number, and how to turn that number into the textual string of digit-characters. 
Making a cell blue, or the text red, or bold - these are all visual transformations that are merely a set of attributes regarding the display of data in a cell.  We don't care here about the type of data in the cell, since we just have to put pixels on a screen. 

So, to bottom-line this: it's all about what you want to happen.  If you're producing HTML reports, then HTML & CSS are very convenient methods for describing the visual-effects formatting of the cell, since you won't have to convert it twice. 
As far as I know, there's only a couple of standards for encoding visual-effects display, and they are similar to SGML - TeX, HTML, PostScript, etc; they all have "tags" (sometimes with "attributes") to modify the display of the content within the tag. 
Which leaves us the transformational formatting.  There were two common approaches to this.  The first is procedural.  You list a set of transformations you wish to do on the data to turn it into text.  Nowadays, we often use substitution masks, like in your example, $#,##0.00, or like in sprintf's %.2f, etc. 
Again, just choose a formatting specifier that is the simplest to use in your environment.  If you're coding in a language that accepts a certain format, then use it!