diff --git a/src/tools/prelude.rs b/src/tools/prelude.rs
index f91c28e9..79fe0fb0 100644
--- a/src/tools/prelude.rs
+++ b/src/tools/prelude.rs
@@ -29,6 +29,7 @@ pub use std::cell::RefCell;
 pub use std::mem;
 
 //UI
+pub use crate::user_interface::gui;
 pub use crate::user_interface::{Interface, MouseInfo};
 pub use imgui::Ui;
 pub use sdl2::mouse::MouseButton;
diff --git a/src/tools/vws/dialog.rs b/src/tools/vws/dialog.rs
index 9c4e653a..1c20bf53 100644
--- a/src/tools/vws/dialog.rs
+++ b/src/tools/vws/dialog.rs
@@ -75,6 +75,11 @@ impl VWS {
             let s_selection = idx_to_cap_type(s_current_selection);
             let e_selection = idx_to_cap_type(e_current_selection);
 
+            if s_selection == CapType::Custom || e_selection == CapType::Custom {
+                gui::error!("Cannot use custom caps at this time from MFEKglif.");
+                return;
+            }
+
             // we only update the contour and previews when our selection changes
             if old_s != s_current_selection || e_current_selection != old_e {
                 let mut new_data = vws_contour;
diff --git a/src/user_interface/gui/mod.rs b/src/user_interface/gui/mod.rs
index 7a6bb7b0..e6aa88cb 100644
--- a/src/user_interface/gui/mod.rs
+++ b/src/user_interface/gui/mod.rs
@@ -39,6 +39,9 @@ use imgui_sdl2::ImguiSdl2;
 use imgui_skia_renderer::Renderer;
 use sdl2::{event::Event, mouse::MouseState, video::Window};
 
+#[macro_use]
+pub(crate) mod msgbox;
+pub(crate) use self::msgbox::gui_error as error;
 pub mod layer_list;
 pub mod prompts;
 
diff --git a/src/user_interface/gui/msgbox.rs b/src/user_interface/gui/msgbox.rs
new file mode 100644
index 00000000..f26bc088
--- /dev/null
+++ b/src/user_interface/gui/msgbox.rs
@@ -0,0 +1,15 @@
+macro_rules! gui_error {
+    ($($format_args:tt),*) => {
+        use log;
+        use msgbox::{self, IconType::*};
+        use std::thread;
+        log::error!($($format_args),*);
+        thread::spawn(|| {
+            match msgbox::create("MFEKglif critical error", &format!($($format_args),*), Error) {
+                Ok(_) => log::trace!("Opened crash msgbox successfully"),
+                Err(e) => log::error!("Failed to create error box! {:?}", e),
+            }
+        });
+    }
+}
+pub(crate) use gui_error;