Item With different length

i have i issue
for example i have item x the default unit of measure is Meter in selling and in buying is roll and the roll have different length like 200 Meter or 150meter i have to issues now first one i want to know the rest of each roll in the stock and whole balance for this item second issue when receive roll in buying i try to give it serial and when i make sales transaction for the item like 50 meter form the roll ask me to enter 50 serial
so i dont know how to fix

any suggestion

Check the below following links, you may find it helpful

Thanks for ur help
but there is something else when i use serial number in receiving roll (roll =100 meter ) enter one serial for the roll and when make sales transaction selling in meter like 10 meter in transaction system asking me to enter 10 serial numbers so how to enter one serial for the roll and sell from it without serial