Fifi, Congratulations of doing 6 months of breastfeeding
I know you asked about formula feeding, but as you didn't say whether or not you wanted to wean your baby, just that you felt you HAD to. So I thought I would post alternatives solutions in case that helps.
On returning to work some mothers :-
: Continue to breastfeed when they are with their baby and put their baby in a nearby child care facility so they can visit baby for a lunch time nurse.
: Continue to breastfeed when they are with their baby and provide nursery with expressed milk for the baby to have during the day. (This assumes you having the time and energy to pump during the day whilst you are at work)
: Continue to breastfeed when they are with their baby and the nursery gives the baby suitable solids, water and NO milk during the day. Some solids can count to your baby's calcium requirements and the baby will nurse more when mother is around (BTW this is known as 'reverse nursing' and might happen anyway, even if the baby is provided with formula or breastmilk during the day)
: Continue to breastfeed when they are with their baby and ask the nursery to formula feed during the day. In this case you can give the nursery the formula and ask them to make it up as the guidelines outline.
If you decided to go to full formula feeding, please make the bottles up properly with hot water of no less than 70c and not how your friend and LittleBoyBlue makes up their bottles.