set repeat_number to 0
repeat
    set theDesktop to POSIX path of (path to desktop as string)
    set theCurrentDate to current date
    set shellCommand to "/usr/sbin/screencapture \"" & theDesktop & "Screen Shot " & theCurrentDate & ".png\""
    do shell script shellCommand
    delay 3
    set repeat_number to repeat_number + 1
    if repeat_number ≥ 199 then
        exit repeat
    end if
end repeat