diff --git a/src/training.jl b/src/training.jl
index c8deb238..f5b4826b 100644
--- a/src/training.jl
+++ b/src/training.jl
@@ -12,21 +12,42 @@ function accuracy(m, data)
   return correct/n
 end
 
-function train!(m, train, test = [];
+"""
+  @cb for ... end t expr
+
+Run the for loop, executing `expr` every `t` seconds.
+"""
+macro cb(ex, t, f)
+  @assert isexpr(ex, :for)
+  cond, body = ex.args
+  @esc t f cond body
+  :(let
+    t0 = time_ns()
+    dt = $t*1e9
+    f = () -> $f
+    @progress $(Expr(:for, cond, quote
+      t = time_ns()
+      if t - t0 > dt
+        t0 = t
+        f()
+      end
+      $body
+    end))
+  end)
+end
+
+function train!(m, train; cb = [],
                 epoch = 1, η = 0.1, loss = mse)
-    i = 0
     @progress for e in 1:epoch
       info("Epoch $e")
-      @progress for (x, y) in train
+      @cb for (x, y) in train
         x, y = tobatch.((x, y))
-        i += 1
         ŷ = m(x)
         any(isnan, ŷ) && error("NaN")
         Δ = back!(loss, 1, ŷ, y)
         back!(m, Δ, x)
         update!(m, η)
-        i % 1000 == 0 && @show accuracy(m, test)
-      end
+      end 5 foreach(f -> f(), cb)
     end
     return m
 end