Clearing Field values on SRM Portal

Folks,

I had added a validation at the level of assigning Substituion in SRM at the level of APPROVAL.

Validation part is working fine but the field values on the FORM page of BSP are not getting cleared after the error message.Due to this it is considering the previous value even when we change the value at the screen level of SRM Portal.The value in the screen field SUBSTITUTE is not getting cleared.

Kindly share your expertise on clearing the field values on FORM Pages of SRM Portal ( 4.0).

Thanks,

K.Kiran.