diff --git a/metplus/wrappers/command_builder.py b/metplus/wrappers/command_builder.py
index 14af04860..9b32b4040 100755
--- a/metplus/wrappers/command_builder.py
+++ b/metplus/wrappers/command_builder.py
@@ -688,6 +688,9 @@ def find_file_in_window(self, level, data_type, time_info, mandatory=True,
             self.log_error('Must set INPUT_DIR if looking for files within a time window')
             return None
 
+        # substitute any filename template tags that may be in _INPUT_DIR
+        data_dir = do_string_sub(data_dir, **time_info)
+
         # step through all files under input directory in sorted order
         for dirpath, _, all_files in os.walk(data_dir):
             for filename in sorted(all_files):