Have you tried to add a parameter to the constructor of your forms?
This can be done in many ways and the code below is just one example:
public class Form2 : Form
{
public Form2(params bool checkBoxValues)
{
InitializeComponent();
if (checkBoxValues.Length > 0)
checkBox1.Checked = checkBoxValues[0];
if (checkBoxValues.Length > 1)
checkBox2.Checked = checkBoxValues[1];
if (checkBoxValues.Length > 2)
checkBox3.Checked = checkBoxValues[2];
}
}
Form2 frm = new Form2(checkBox1.Checked, checkBox2.Checked, checkBox3.Checked);
frm.ShowDialog();