If I am reading you correctly, you have a form (lets call it "fromDisplayUsers") and when you press the "New User" button, you bring up another form to get the user data ("formCreateUser"). When the user presses the "Ok" button on "formCreateUser", it closes the form and you need the data to be available in "formDisplayUsers".
This is a normal thing to do, and the best way to handle it is to set up
public
properties in formCreateUser which access the information entered by the user. So, if the username is enetered into a TextBox called tbUserName:
public string Username
{
get { return tbUserName.Text; }
set { tbUserName.Text = value; }
}
So, formDisplayUsers:
...
formCreateUser fcu = new formCreateUser();
fcu.UserName = "Type your name here";
fcu.ShowDialog();
string myUserName = fcu.UserName;
Repeat this for all the user values you need, and you can then insert them into the datagrid as normal.
Using
public
properties is recommended, because it means that formDisplayUsers does not need to know anthing about how fromCreateUser works: You can change it as you like as long as it continues to return a string for the user name.