diff --git a/luca_pak/src/lib.rs b/luca_pak/src/lib.rs
index ce88517..3a98d97 100644
--- a/luca_pak/src/lib.rs
+++ b/luca_pak/src/lib.rs
@@ -25,6 +25,9 @@ pub enum PakError {
 
     #[error("Malformed header information")]
     HeaderError,
+
+    #[error("Index not found")]
+    IndexError,
 }
 
 /// A full PAK file with a header and its contents
@@ -196,7 +199,10 @@ impl Pak {
         })
     }
 
-    pub fn encode<T: Write + Seek>(&self, mut output: &mut T) -> Result<(), PakError> {
+    pub fn encode<T: Write + Seek>(
+        &self,
+        mut output: &mut T
+    ) -> Result<(), PakError> {
         let mut block_offset = 0;
         self.header.write_into(&mut output)?;
 
@@ -250,6 +256,34 @@ impl Pak {
         Ok(())
     }
 
+    pub fn replace(
+        &mut self,
+        index: usize,
+        replacement_bytes: &[u8]
+    ) -> Result<(), PakError> {
+        let block_size = self.header().block_size();
+
+        let replaced_entry = if let Some(entry) = self.entries.get_mut(index) {
+            entry
+        } else {
+            return Err(PakError::IndexError)
+        };
+
+        // Replace the entry data
+        replaced_entry.data = replacement_bytes.to_vec();
+        replaced_entry.length = replaced_entry.data.len() as u32;
+
+        let mut next_offset = replaced_entry.offset + replaced_entry.length.div_ceil(block_size);
+
+        for entry in self.entries.iter_mut().skip(index + 1) {
+            entry.offset = next_offset;
+
+            next_offset = entry.offset + entry.length.div_ceil(block_size);
+        }
+
+        Ok(())
+    }
+
     /// Get the header information from the PAK
     pub fn header(&self) -> &Header {
         &self.header
diff --git a/luca_pak/src/main.rs b/luca_pak/src/main.rs
index 97184b9..ff26529 100644
--- a/luca_pak/src/main.rs
+++ b/luca_pak/src/main.rs
@@ -1,4 +1,4 @@
-use std::{fs::File, io::BufWriter};
+use std::{fs::File, io::{BufWriter, Read}};
 use luca_pak::Pak;
 
 fn main() {
@@ -38,14 +38,19 @@ fn main() {
     }
     */
 
-    let pak = Pak::open("MANUAL.PAK").unwrap();
-    println!("{:#?}", pak.header());
+    let mut pak = Pak::open("MANUAL.PAK").unwrap();
+    //println!("{:#?}", pak.header());
     //println!("{:#032b}", pak.header().flags().0);
 
+    /*
     for (i, entry) in pak.entries().iter().enumerate() {
-        //println!("{i:03}: {:06.2} kB - {}", entry.len() as f32 / 1_000.0, entry.name().as_ref().unwrap());
+        println!("{i:03}: {:06.2} kB - {}", entry.len() as f32 / 1_000.0, entry.name().as_ref().unwrap());
         entry.save("./output/").unwrap();
     }
+    */
+
+    let rep_cz_data: Vec<u8> = std::fs::read("en_manual01_Linkto_2_6").unwrap();
+    pak.replace(4, &rep_cz_data).unwrap();
 
     let mut output = BufWriter::new(File::create("MANUAL-modified.PAK").unwrap());
     pak.encode(&mut output).unwrap();