Combining multiple cell information into one cell
 

There are two tiers to this problem. Cells A11:A26 are showing numbers 1
through 16. Cells B11:B26 are product names relating to the numbers 1
through 16. The numbers in A11:A26 are just reference numbers. In cells
B11:B26, each cell is a drop down list of product names. Cells C11:C26 are
costs associated with the product names. The first question is, when I
select the products from each drop down list in each cell (B11:B26), I want
all the numbers (A11:A26)corresponding with the selected cells (B11:B26) to
show in cell C37. I am wanting to show and separate all the numbers in the
one cell with a comma or a plus sign. Second question is based on the
selection in cell C37, I want to total all product costs associated with the
numbers showing in C37. Can anyone help me with this task. Can it be done?
Thanks in advance for any help.