this was probably a bad idea because they need to be actors for events to work

Source/MyProject/Private/MagicFloatInput.cpp

@@ -15,4 +15,9 @@ void UMagicFloatInput::HandleOnTextCommitted(
     x = FCString::Atod(*inText.ToString());
 
   SetText(FText::FromString(FString::Printf(TEXT("%.7f"), x)));
+  HandleMagicFloatsMangledEvent();
+}
+
+void UMagicFloatInput::HandleMagicFloatsMangledEvent() {
+  OnMagicFloatsMangled.ExecuteIfBound();
 }

Source/MyProject/Private/VerifierTextBlock.cpp

@@ -1,5 +1,12 @@
 // Fill out your copyright notice in the Description page of Project Settings.
 
-
 #include "VerifierTextBlock.h"
 
+void UVerifierTextBlock::NativeOnInitialized() {
+  if (destInput != nullptr) {
+    destInput->OnMagicFloatsMangled.BindUObject(
+        this,
+        &UVerifierTextBlock::verifyFloats
+    );
+  }
+}

Source/MyProject/Public/MagicFloatInput.h

@@ -7,6 +7,8 @@
 #include <Components/TextBlock.h>
 #include "MagicFloatInput.generated.h"
 
+DECLARE_DELEGATE(FOnMagicFloatsMangledDelegate);
+
 /**
  *
  */
@@ -22,4 +24,12 @@ class MYPROJECT_API UMagicFloatInput : public UEditableTextBox {
 
   UPROPERTY(EditAnywhere)
   UTextBlock * sourceInput;
+
+  UPROPERTY(EditAnywhere)
+  UTextBlock * myVerifier;
+
+  UFUNCTION()
+  void HandleMagicFloatsMangledEvent();
+
+  FOnMagicFloatsMangledDelegate OnMagicFloatsMangled;
 };

Source/MyProject/Public/VerifierTextBlock.h

@@ -4,14 +4,24 @@
 
 #include "CoreMinimal.h"
 #include "Components/TextBlock.h"
+#include "MagicFloatInput.h"
 #include "VerifierTextBlock.generated.h"
 
 /**
  *
  */
 UCLASS()
-class MYPROJECT_API UVerifierTextBlock : public UTextBlock
-{
+class MYPROJECT_API UVerifierTextBlock : public UTextBlock {
+
   GENERATED_BODY()
 
+  UPROPERTY(EditAnywhere)
+  UTextBlock * sourceInput;
+
+  UPROPERTY(EditAnywhere)
+  UMagicFloatInput * destInput;
+
+  void verifyFloats();
+
+  void BeginPlay() override;
 };