[brasarehot]

Ok this is kind of a long question... [Note: uM means micro molar, uL means micro liter]
Tube 1 has initial concentration of 100uM of "X", Tube 2 has initial volume of 240uL of Buffer.
I want to go from a final "X" concentration of 0.01uM to a final "X" concentration of 0.033uM instead, when I add some of Tube 1 into Tube 2, how do I do it?
So here's my thinking so far... where V1 is initial volume and V2 is final volume
M1V1=M2V2, 100uM(V1) = 0.033uM(240uL + V1), therefore V1 = 0.079 = 0.08uL approximately. 
Therefore I need to add 0.08uL of an initial "X" concentration of 100uM.
But my pipette range is 0.1 - 2.5uL, and 0.08uL is too small for this range so I figured I would take 0.8uL  .
Now I'm stumped after this... Do I have to get a 3rd tube and add water to the 3rd tube along with "X"?
If someone could help me step by step with this part, I would greatly appreciate it. And please show each math step.

[Dan]

You could approach it from the other direction. Choose a volume of your X solution that you can accurately measure - e.g. 1.0 uL - and calculate how much buffer you need to dilute it with to bring the concentration to 0.033 uM.

i.e. (100 uM)(1.0 uL) = (0.033 uM)(V_buffer+0.1)

Solve for V_buffer