easy question about tag shortcuts

hi all –

sorry for such an easy brain-dead question, but i am sorta sick today and the brain is not fully functioning.

when i insert a media-image, first i switch from “visual” to “text”, and then i insert the following code to “float” the image to one side or the other:

<div style='float:left;'>
<img stuff… />
</div>

i am wondering how to have some sort of environmental variables set (or is it a ‘macro’ ?) , so i can do something like:

STARTFLOATLEFT = <div style='float:right;'>
ENDFLOATLEFT = </div>

and then use the following in the page/post instead:

[STARTFLOATLEFT]
<img stuff….>
[ENDFLOATLEFT]

for a bonus extra-credit point, please help me to pass in ‘right’ or ‘left’ into the environmental variable from the shortcut:
[STARTFLOAT(“left”)]

thank you, and i apologize for the brain-dead question.