I am sure it is possible with a formula, but it would have to consider a lot of possiblilities and hopefully the data is limited (i.e., nothing over $1000 and nothing negative).
Basically the number would have to broken down by hundreds, tens, ones and cents. Put through a series of if statements or a switch statement (for each group - hundreds, tens, etc.) to get a string and then combine the seperate strings back to one string.
Lots of luck.