Enhancement for ME21N
My customer gives me a requirement is that when the end user uses ME21N to create a purchase order,he/she inputs the data and then click the button "save" to save the data,then it needs to check whether the vender is valid or not.If the vender is valid,then the end user can save data.Otherwise,we should not create the purchase order.
I find out many customer functions and some BADIs,but I don't know which enhancement I should use.Could you please help me to find out which enhancement I should use??
Thanks a lot.