Using Applescript to paste the current date into a range of Excel cells
I think the code below speaks for itself. The do shell script command shouldn't be used inside another application tell block. Still I prefer a vanilla AppleScript solution as below which is fine to be used in any context in the script. 

tell (current date) to set {_day, _month, _year} to {day, it's month, year}
set _day to text -2 thru -1 of ("00" &amp; _day) -- add leading zeros if needed
set _month to text -2 thru -1 of ("00" &amp; (_month as integer)) -- add leading zeros if needed
set _date to _day &amp; "/" &amp; _month &amp; "/" &amp; _year

tell application "Microsoft Excel"
    tell workbook 1
        tell worksheet 1
            set value of range "$A1:A10" to _date
        end tell
    end tell
end tell