problem with decimal places

I want the size of selected file/folder in MB and GB.
I want them to be in two decimals (and no decimal places if both decimal places are zeroes).
2480.83 MB
2.48 GB

260 MB
0.26 GB )
The below script sometimes gives me result like

4.391844E + 4 MB
42.89 GB
Please help me correct it.

set newline to ASCII character 10
tell application "Finder"
	repeat with aitem in (get selection)
		set textString to (size of aitem) / (1024 * 1024 / 100)
                set textString to round textString
		set textString1 to (textString / 100) & " MB" as text
		set textString2 to (round (textString / 1024)) / 100
		set textString2 to (textString2 & " GB") as text
		set textString3 to textString1 & newline & textString2
		end repeat
end tell


try this

tell application "Finder" to set theSize to size of disk 1

set textString1 to formatSize(theSize, "MB")
set textString2 to formatSize(theSize, "GB")
set textString3 to textString1 & return & textString2

on formatSize(value, mode)
	if mode = "MB" then
		set value to value / (1024 ^ 2)
	else if mode = "GB" then
		set value to value / (1024 ^ 3)
	end if
	if value > 1000.0 then
		return ((round value) as text) & space & mode
		return (((round (value * 100)) / 100) as text) & space & mode
	end if
end formatSize

When i modified it to get size of selection instead of size of disk1 by adding

tell app "Finder" to repeat with aitem in (get selection)
set theSize to the size of aitem

i got some error saying cannot continue “formatSize”

That’s because the handler call in now in an application tell block.
Either keep it outside or put the keyword my in front of the handler call

thanks. It worked.