Question about Licences Contracts - Activate/Reactivate Licenses

HI,

We have many softwares acquired licenses in Microsoft Eopen who want to add on Servicedesk to manage licenses and when the licenses expires (Microsoft Office 2003/2007/2010, etc).

Situation:

1) We add an license using the option Softwares Licenses without fill the dates (start date and end date). I control the dates by license contracts (association license with contract).

2) When we do this action, the license that didn't have the date takes the date of contract. If we edit the license, the date is already filled and you can't erase.

3) If the contract has expired, the license also appears as expired. Once the license is expired you can not reactivate.

Is there any way to control the contracts associated with the licenses and control the date?

Thanks.

Lincon