in C1:C10 I have the production cost per unit (vlookup based on value in
Col B)

The use of the "VLookup" function indicates to me that you will have a hard
time using Solver. This causes a "Jump" in the production costs, and Solver
can not proceed from there. My guess is that you will have to change your
model so that the production costs are better approximated with a continuous
function, vs. a "discontinuous function" via VLookup. Using Integer
constraints in your model is often a workaround for "VLookup." Solver then
should be able to help from there.

HTH
Dana DeLouis

"Allan" wrote in message
...
Hi
I have a list of 10 plants. Each plant has a different incremental cost
of production. In B1:B10 I have a production rate, in C1:C10 I have the
production cost per unit (vlookup based on value in Col B) in D1:10 is the
production cost per plant. B11 is the Total production rate and D11 is the
total production cost. If I need to increase production, how can I detemine
the most economical production rate for each plant while also keeping the
total production cost at a minimum. Can this process be automated and
assigned a button to calculate production rates
Thanks!
Allan