i take 500mg metformin and 2.5mg of glyburide twice a day i go to curves 5 days a week to exerise bu

Depends what time of evening- if it's post prandial (2 hours after you eat), then you can modify your dinner meal, either by eating less carbs, or by adding vinegar (salad with heavy vinegrette), or by adding more soluble fiber (beans/peas/nuts/fruit skin(apple/orange)/carrots), or fat (fish or vegetable).  If it's later, some exercise if possible.  And if overnite, you might need some insulin, but only if you have lost weight or your A1C is over 6.5 (trending up).

As far as your meds, you may do better with prandin instead of glyburide.  Prandin is like glyburide, but it helps release insulin after a meal.  So again, if you're 270 2 hours after dinner, consider switching to prandin (although it's more $ than glyburide).  Best of luck- anyone who does curves every day has good discipline :)

for how long are you exercing is important. I also take 500mg metformin and i do fast walking every eveining for 50mints(But 7 days a week). I found  in the intial stages my fasting sugar levels were increased than normal, they were 155-160. But sustained effort for 3 months of continous exercise it is comming low to 120-130. So my advise is do not worry, keep continue doing exercise, time taken may differ from body to body. All the best.