I assume you mean delete all fiels except that last 10 days worth?
needs DirPlus(), FlipCTime(), and TimeConvert()

Code:

$folder = "%temp%"
for each $file in dirplus($folder,"/a-d")

	$Filedate = split($file.datelastmodified)
	$filedate[1] = timeconvert($filedate[1]+" "+ $filedate[2])

	$filedate[0] = split($filedate[0],"/")

	$filedate = flipctime($filedate[0][2]+"/"+$filedate[0][0]+"/"+$filedate[0][1],$filedate[1])

	if $filedate <= flipctime(@date,@time) - 864000 ;the number of seconds for 10 days
		? "10+ days old " "	" $file.name "	" $file.datelastmodified
	endif
next