Applescript to align photos in PowerPoint - Please Help!

Hello,

I have the below applescript and I want it to align the photos that I have in Powerpoint (1 photo per slide) to center them all.

Please tell me what I am doing wrong.

Thanks.

tell application “Microsoft PowerPoint”
activate
set thePres to active presentation
set slideCount to count slides of thePres
repeat with a from 1 to slideCount
set theShape to first shape of slide a of thePres
set width of theShape to (8 * 70)
set alignment of every slide of active presentation to align shape center – This is not working!!!
end repeat
end tell