restric the K2 plan button to submit form

Hi , i am new to K2,

is there is any possibility to restrict or stop the K2 button to submit the form for further process on certain criteria

for example,

there is a field at form which is mandatory for a user to fill, if user didn't fill it and submit the form, the K2 smart form submit the form to server.

but in ideal scenario , the application has to restrict the user to perform any other operation.

But when submit the form its sends the form information to server.

Please Help.

Regards

Zahid