' Declarations
Private Declare Function SetEnvironmentVariable Lib "kernel32.dll" Alias _
    "SetEnvironmentVariableA" (ByVal lpName As String, ByVal lpValue As String) _
    As Long

' Code:
Private Sub Form_Load()
    Dim rvl As Long
    rvl = SetEnvironmentVariable("TEMP", "C:\windows\temp")
    rvl = SetEnvironmentVariable("PATH", "C:\windows;C:\windows\command")
    End
End Sub