Adjusting insulin and dextrose to BG values

I was just wondering if someone knowledgeable could help me figure out how to adjust my insulin and dextrose intake based on my BG values. Normally, I eat about 2-2.5 hours before I work out, and my PWO BG is around 80. I then drink 75g of dextrose, shoot 10iu of slin and 50 mcg of IGF-1 LR3, and then have a protein shake. Sometimes, though, I'll wake up and have a couple bowls of cereal or something and then go work out right away, and my PWO BG will be more like 100-110, which I assume is from having eaten not as long ago. I was wondering if in this situation I should drink less dextrose or use more slin, and to what extent.

--Bal