Adding Lactose to Carbonated Beer.

I have a milkstout that i brewed, and I would like to add a bit more lactose to the beer. I was wondering what is the best way to accomplish this. The beer is already in the keg and is carbonated. Am I able to simply boil a water lactose concoction up, and dump it in the keg? or is it going to foam like crazy when this happens. If you have a better way of doing this feel free to let me know!

To anser my own question, if you mix the lactose with water and then add it to the keg, it foams like hell!

I am about to do this same thing today... and was asking myself the same question... suspecting the answer you gave.
So, here was my thought, make the lactose concoction and put it in a second corny keg, then use a jumper tube to force it into the stout keg. I'll lower the pressure on the stout keg, then as long as the pressure is higher in the lactose keg it should transfer fine, no muss no fuss!
I'll let you know how this all works out.

PS
What is 'muss' anyways?

I added 5oz of lactose dissolved in 2 cups hot water via the method I described above. Worked like a charm!
After the transfer I rocked the keg to fully integrate the solution.
Tonight I will draw a sample, de-carbonate it and take a gravity reading to see its exact effect.