Yes it can be done, I got a loan of miles to book a free return flight.
Here is the email from a very nice person from emirates.

one thing i must add, Never give up when they say no, It works

Thank you for your email. As per below, A total of 104500 miles is required for a return flight from Manchester to Bangkok with a Saver miles for the outbound flights and return in Flex when booked online as you benefit of a 5% online discount. You will earn the miles for your trip in February once you starts your flight and reach your destination and the same for the return. Therefore If you wish to use the miles you will earn from this trip toward the required 104500 miles for the trip in August you wish to book with your miles then this can only be done once you complete your February trip to enable the miles to be added to your account. As per skywards T&Cs, members are eligible to earn miles only once they reach their destination and not when they buy the ticket. We are willing to adjust your account with the missing miles to enable you to book online. Once your flights are booked we will then take the adjustment off , then your account will go into negative until you complete your trip in February and the miles will be earned so the balance will be adjusted to normal. If you happy with my feedback please revert back so we can adjust your account to enable you to book online straight away or wait until you complete your flights, earn the miles and then make the online booking ,Bearing in mind that flights availability for August is subject to change at any time. I hope this information is useful to you and thank you for your support of the Skywards programme. Should you have any further queries please do not hesitate to contact us.