Feeding source with various demand quantity for different parts

Hi,
In my model, i have 15 different parts and each has different demand quantity for every month and the demand is for one year (from April to March). The above demand will be fed to source at the beginning of every month for all the 15 different parts. These 15 parts are processed in three machines on FIFO basis.

My concern is
1) i want the source to take the demand quantites of 15 parts at the beginning of a month and divide each parts quantity by 2 (value should be rounded off) and the source should fed the first half quantites of 15 parts first and then fed the second half quantites of 15 parts. After completing the first month total demand quantites, the source should take second month quantity and do the same above procedure and the model should run for 12 months.
2)i want the source to read the demand quantites of 15 parts for 12 months from the excel file directly and not from the global table. Is there any flexsim program codes for the above.

Kindly help me out to solve my problem
Thanks