(of course, in ‘real life’ that foot or feet field would be hidden by setting the visibility to admins)

then when you’re building your email/view/pdf/whatever just insert that field wherever you need the conditional text.

(and obviously this is fast and dirty – I’m not messing w/ decimal places and rounding and such, just being lazy and restricting the donation amount field to minimum of 20 w/ steps of 20, but hopefully it might point you in a direction that you can get it working…)

<script type="text/javascript">
// my Form field keys are:
// Square feet sponsored: 54p4h
// Foot or feet: fycdf
// change yours in all places as appropriate... 
//get the number of sq feet sponsored
var val1 = $("#field_54p4h").val();
//set the foot or feet based on the sponsored amount
//if it's equal to 1 set it to foot
if (val1 == 1)
//if larger than 1 set it to feet
else if (val1 > 1)
//make it so

stick that in the form settings / customize html / after fields