Use the SHFormatDrive API function.

Private Sub FormatDisk(ByVal options As Long)
Dim drive_letter As String
Dim drive_num As Long
Dim status As Long

    drive_letter = UCase$(Left$(txtDrive.Text, 1))
    drive_num = Asc(drive_letter) - Asc("A")
    status = SHFormatDrive(hWnd, _
        drive_num, 0, options)
    Select Case status
        Case -1
            MsgBox "Format failed. User pressed Close."
        Case -2
            MsgBox "Format canceled. User pressed Close."
        Case -3
            MsgBox "Unable to format this disk."
        Case 6
            MsgBox "Disk formatted."
        Case Else
            MsgBox "Unknown return status " & _
                Format$(status)
    End Select
End Sub