Running game C# visual studio windows form

i am currently making a running game for my college assingment using c# with visual studio 2011, currently i managed to make my character jump but i need to make it jump more than once can someone help me with the code?i would appreciate any kind of help

thanks

this is my code for making my player jump

in FormKeyDown

if (jump == false)

{

if (e.KeyCode == Keys.Space)

{

jump = true;

force = gravity;

}

in timer

if(jump)

{

player.Top -= force;

force--;

}

if(player.Top + player.Height >= screen.Height)

{

player.Top = screen.Height - player.Height;

jump = false;

}

else

{

player.Top += 1;

}