Dear,

My requirement is to deactivate the old condition when a new one (same condition) is entered manually ?

If you explain your requirement to ABAPer then he will accomplish like below ( not sure success or not by this solution ) .

When you have Old Condition Type with Condition Record in Sales Order then If you need to increase or decrease the amount of that Condition Type by manually  in Sales Order then Deactiavte the Old Condition Type and Activate the New Condition Type .

Note : Already all users has explained on this requirement as they had an Idea on it .Like ,I have proposed above .

Thanks,

Naren