diff --git a/missense_kinase_toolkit/databases/missense_kinase_toolkit/databases/utils.py b/missense_kinase_toolkit/databases/missense_kinase_toolkit/databases/utils.py
index 97a6072..c28966d 100644
--- a/missense_kinase_toolkit/databases/missense_kinase_toolkit/databases/utils.py
+++ b/missense_kinase_toolkit/databases/missense_kinase_toolkit/databases/utils.py
@@ -183,3 +183,10 @@ def get_repo_root():
         return repo.working_tree_dir
     except git.InvalidGitRepositoryError:
         return None
+
+
+def try_except_substraction(a, b):
+    try:
+        return b-a
+    except TypeError:
+        return None
\ No newline at end of file