Multiple Signatures

Hi

First let me explain my scenario i had done so far and then i will explain the problem i am facing.

Scenario

I had created an intercative form with 4 Text Fields along with two signature fields(So that the form has to be signed by two persons let it be User1, User2).

The first two text fields (TextField_1 and TextField_2) will be filled by the User_1 and then User_1 will sign in the First Signature field.

The next two text fields (TextField_3 and TextField_4) will be filled by the User_2 and then User_2 will sign in the Second Signature field.

This is my scenario so far i had done.

Problem i am Facing

The User_1 will fills the value and sign the form and later when the user_2 fills the data and signs the form, the first signature is showing an question mark and exclamatory mark indicating that form had undergone some changes.

Solution type needed

I want a solution in such a way that whenever the user_2 signs the form the status of the signature field_1 should not be changed any more.

Plz suggest how to achieve this

Thanks In Advance...

Regards
Chandran S