Is it possible to post a good issue movement before post the good receipt

Question

Is it possible to post a good issue movement before post the good receipt  movement for the same material, into the same period?
We try to explain better, today we've done a test:
Step 1 :   We have created a material, wich material type is HAWA, with price control V, and 1 euro for 1 ST.
Step 2 :   We have post a good receipt movement, 561 of this material  with 1000 ST of stock, and on posting date: 05.05.2011.
Step 3 :   Then, we have post a good issue movement, 562 of the same material, with 500 ST of stock,  on posting date: 01.05.2011 ( so that, the posting date of the 562 is before from the posting date of 561).
And it has worked, so that on trx "mb51" for this material we saw:
PLANT1           STO1         562           Mat. Doc.1           01.05.2011            500-  ST
PLANT1           STO1         561           Mat. Doc.2           05.05.2011           1000  ST
And with "fbl3n" for this G/L account , the same situation:
G/LAccount1            DocumentNo1            01.05.2011        99            500-  EUR
G/LAccount1            DocumentNo2            05.05.2011        89            1000  EUR
We don't like this fact, someone knows how is it possible? The negative stocks aren't flagged!!!!
Edited by: Ariana Serrano Aguila on May 5, 2011 5:50 PM

Answer 1

SAP only checks if there is enough quantity in the period (month), it does not check if there is enough stock at date level.
there is no stock stored in any table for a given date. SAP would need to run the logic of MB5B to calculate the stock at a certain date, this would cause tremendous performance issues.
you either have to do this calculation yourself in a user exit, or you better train your users.