Level Load

I am trying to use microsoft solver to assign different jaw types to the different machines by minimizing jaw changeovers. I have some constraints in microsoft solver that I need it to meet, but then in the variable cells C2:H13 I am not sure what formula I need for each cell constraint to say that if this machine can run this jaw type then assign all hours to it if it is equal to or less than 13 hours. And if it is greater than 13 hours then I would assign 13 hours to that machine, and the secondary machine will take the remaining hours if it meets the other constraints. In cells I2:I13 I have individual constraints saying that the sum in columns C:H for that row has to equal the value in the respective cell in column B. Then in Cells C14 through H14 I have a formula saying sum of rows 2 through 13. And in the constraint I have each cell saying that the sum is equal to or less than 13. In M2 through S28 I have what machines can run what jaw type by priority. P is primary, then S1 through S3 are secondary with S1 given priority before S2