diff --git a/bin/curvecalc b/bin/curvecalc
--- a/bin/curvecalc
+++ b/bin/curvecalc
@@ -233,7 +233,10 @@ def sub_commands_tk(master, curveset, su
     tk.Button(f, text="reload subs (C-r)", 
         command=reload_subs).pack(side='left')
     tk.Button(f,text="new subterm named:", command=add_cmd).pack(side='left')
-    tk.Entry(f,textvariable=newname).pack(side='left',fill='x',exp=1)
+    entry = tk.Entry(f, textvariable=newname)
+    entry.pack(side='left', fill='x', exp=1)
+    entry.bind("<Key-Return>", lambda evt: add_cmd())
+
     return f
     
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