This bit of code will allow you to detect key presses while the form is not the active window. I currently use this for macros and for my trainer programs for turning on cheats.

All you need to have is a timer on the form. You can either drag and drop one on the form or declare it in code and write the timer.Tick event.

In this example I check for 2 key presses.

Code:
    Dim altkey As Boolean

    Dim Num_1 As Boolean

    Dim Num_2 As Boolean

    Dim Num_3 As Boolean

    Private Sub tmr_Keys_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tmr_Keys.Tick

        altkey = GetAsyncKeyState(Keys.LMenu)

        Num_1 = GetAsyncKeyState(Keys.NumPad1)

        Num_2 = GetAsyncKeyState(Keys.NumPad2)

        Num_3 = GetAsyncKeyState(Keys.NumPad3)

        If altkey And Num_1 = True Then 'Infinite Health Player 1

            btn_P1InfiniteHealth_Click(sender, e)

        ElseIf altkey And Num_2 = True Then

            btn_P1InfiniteKi_Click(sender, e) ' Infinite Ki Player 1

        ElseIf altkey And Num_3 = True Then

        End If

    End Sub