diff --git a/src/blocks/custom.js b/src/blocks/custom.js
new file mode 100644
index 0000000..f38cd0e
--- /dev/null
+++ b/src/blocks/custom.js
@@ -0,0 +1,29 @@
+var events = require("../events.js");
+
+module.exports =  {
+  name: "Custom Code",
+  inputs: {
+    inp1: "1",
+    inp2: "2",
+    inp3: "3",
+    inp4: "4",
+    inp5: "5"
+  },
+  output: true,
+  execute: function(inputs, block){
+    eval("customFunc = function(inp1, inp2, inp3, inp4, inp5){" + block.properties.code + "}");
+    return customFunc(inputs.inp1, inputs.inp2, inputs.inp3, inputs.inp4, inputs.inp5);
+  },
+  pageBlock: {
+    html: "To access inputs, use vars inp1, inp2, etc<br><textarea name='code'></textarea>",
+    js: function(block){
+      if(block.properties.code){
+        block.elem.find("textarea").val(block.properties.code);
+      }
+      $(block.elem).find("textarea").keyup(function(){
+        block.properties.code = block.elem.find("textarea").val();
+        events.emit("inputChanged");
+      });
+    }
+  }
+}
diff --git a/src/blocks/index.js b/src/blocks/index.js
index 7bb7577..5b1b788 100644
--- a/src/blocks/index.js
+++ b/src/blocks/index.js
@@ -18,6 +18,7 @@ var blocks = [
   "transpositionReverse",
   "substitution",
   "frequency",
+  "custom",
 ];
 
 module.exports = blocks.reduce((blocks, block)=>{
diff --git a/src/outputCalculation.js b/src/outputCalculation.js
index 35d710b..2cb7d04 100644
--- a/src/outputCalculation.js
+++ b/src/outputCalculation.js
@@ -14,10 +14,7 @@ function resolveOutput(block, cache){
     }
   }
 
-  var output = "";
-  if(Object.keys(blocks[block.type].inputs).length == Object.keys(inputValues).length){ //only execute if all inputs are present
-    output = blocks[block.type].execute(inputValues, block);
-  }
+  var output = blocks[block.type].execute(inputValues, block);
   cache[block.id] = output;
 
   return output;