It depends on your baby ime.
I have done the same thing with both DC with different results.
I started bottlefeeding from day 1 (medical reasons meant that both had to be given formula when born)and gave one (expressed) bottle a day, breastfeeding the rest.
DS (2 years old) was quite happy to receive all forms. But the milk had to be nice and warm (and after hospital he was never keen on formula but would drink it if nothing else was on offer).
DD (13 weeks) will not take it anymore. Accepted it begrudging in hospital, but always latched on straightaway after, much to the nurses' surprise), but by 6 weeks refused it (whatever the bottle, whatever the teat) completely and would rather starve. A problem, what with me back at work and all.
Our solution has been to feed her with a spoon. Timeconsuming and messy, but it works (nursery hates me!). Hopefully in a month or so she'll be sitting up and we can try a cup.
Good luck, but be warned that DD just hates the feel of plastic (won't have a dummy either), and quite literally will go withhout until Mammy shows up. I hope you have more success than me.