Yeah as above the ideal is to get the right spoke length but it can be done with uniform spokes.
If you do have to use same length spokes these araya nipples can help a bit as they have more thread to work with when buying the 14mm and 16mm ones (i.e. they're not just same amount of thread with an extra sleeve as other longer nipples can be). Good luck :)
P.S. I've used the 14mm to build successfully with a similar discrepancy and the wheel's been going strong for 2 years, it's true and never had nipple failure. I haven't tried the 16mm's though.
Yeah as above the ideal is to get the right spoke length but it can be done with uniform spokes.
If you do have to use same length spokes these araya nipples can help a bit as they have more thread to work with when buying the 14mm and 16mm ones (i.e. they're not just same amount of thread with an extra sleeve as other longer nipples can be). Good luck :)
P.S. I've used the 14mm to build successfully with a similar discrepancy and the wheel's been going strong for 2 years, it's true and never had nipple failure. I haven't tried the 16mm's though.
http://www.rocknrollbikes.com/bmx/hubs-spokes-nipples/araya-alloy-nipples-14-gauge-x-12-14-16mm-long.html#Colour%20Option=Red&Length=12%20mm.