diff --git a/pyzebra/app/panel_ccl_integrate.py b/pyzebra/app/panel_ccl_integrate.py
index a4c122f..16f219b 100644
--- a/pyzebra/app/panel_ccl_integrate.py
+++ b/pyzebra/app/panel_ccl_integrate.py
@@ -74,10 +74,10 @@ def create():
         ccl_path = os.path.join(PROPOSAL_PATH, new.strip())
         ccl_file_list = []
         for file in os.listdir(ccl_path):
-            if file.endswith(".ccl"):
+            if file.endswith((".ccl", ".dat")):
                 ccl_file_list.append((os.path.join(ccl_path, file), file))
-        ccl_file_select.options = ccl_file_list
-        ccl_file_select.value = ccl_file_list[0][0]
+        file_select.options = ccl_file_list
+        file_select.value = ccl_file_list[0][0]
 
     proposal_textinput = TextInput(title="Enter proposal number:", default_size=145)
     proposal_textinput.on_change("value", proposal_textinput_callback)
@@ -100,16 +100,34 @@ def create():
         scan_table_source.selected.indices = []
         scan_table_source.selected.indices = [0]
 
-    def ccl_file_select_callback(_attr, _old, new):
+    def ccl_file_select_callback(_attr, _old, _new):
+        pass
+
+    file_select = Select(title="Available files:")
+    file_select.on_change("value", ccl_file_select_callback)
+
+    def file_open_button_callback():
         nonlocal det_data
-        with open(new) as file:
-            _, ext = os.path.splitext(new)
+        with open(file_select.value) as file:
+            _, ext = os.path.splitext(file_select.value)
             det_data = pyzebra.parse_1D(file, ext)
 
         _init_datatable()
 
-    ccl_file_select = Select(title="Available .ccl files")
-    ccl_file_select.on_change("value", ccl_file_select_callback)
+    file_open_button = Button(label="Open", default_size=100)
+    file_open_button.on_click(file_open_button_callback)
+
+    def file_append_button_callback():
+        with open(file_select.value) as file:
+            _, ext = os.path.splitext(file_select.value)
+            append_data = pyzebra.parse_1D(file, ext)
+
+        pyzebra.unified_merge(det_data, append_data)
+
+        _init_datatable()
+
+    file_append_button = Button(label="Append", default_size=100)
+    file_append_button.on_click(file_append_button_callback)
 
     def upload_button_callback(_attr, _old, new):
         nonlocal det_data
@@ -119,7 +137,7 @@ def create():
 
         _init_datatable()
 
-    upload_button = FileInput(accept=".ccl")
+    upload_button = FileInput(accept=".ccl,.dat")
     upload_button.on_change("value", upload_button_callback)
 
     def append_upload_button_callback(_attr, _old, new):
@@ -577,10 +595,14 @@ def create():
         ),
     )
 
-    upload_div = Div(text="Or upload .ccl file:")
-    append_upload_div = Div(text="append extra .ccl/.dat files:")
+    upload_div = Div(text="or upload file:")
+    append_upload_div = Div(text="append extra files:")
     tab_layout = column(
-        row(proposal_textinput, ccl_file_select),
+        row(
+            proposal_textinput,
+            file_select,
+            column(Spacer(height=19), row(file_open_button, file_append_button)),
+        ),
         row(
             column(Spacer(height=5), upload_div),
             upload_button,