Restrict Negative Sales

Hi all,

1. How can we restrict user from entering NEGATIVE quantity in SALES?

Based on my searching, we can set .01 of Return Limit. This method can work when user doing Sales. However, user cannot do Return even they have right to do so.

2. How can we restrict user from entering POSITIVE quantity in RETURN?

Based on my testing, if I purposely put positive value during Return, system will deduct quantity from system (treat as Sales).