Problem changing parameters on button click

I want to have different buttons that dynamically change parameter values.
I have a button that when clicked executes this:
protected void ImageButton1_Click(object sender, ImageClickEventArgs e)
    {
          e.Command.Parameters["VoucherID"].Value= "8";
    }
This doesn't work because ImageClickEventArgs e has no reference to command.
The only way I can get VWD to stop throwing errors is to change 'ImageClickEventArgs' to 'SqlDataSourceCommandEventArgs'
protected void ImageButton1_Click(object sender, SqlDataSourceCommandEventArgs e)
    {
          e.Command.Parameters["VoucherID"].Value= "8";
    }
But this obviously throws errors once run.
Any help please?
 
...