diff --git a/src/dexorder/blockstate/blockdata.py b/src/dexorder/blockstate/blockdata.py
index dd20741..79cfe3c 100644
--- a/src/dexorder/blockstate/blockdata.py
+++ b/src/dexorder/blockstate/blockdata.py
@@ -1,7 +1,6 @@
 import logging
-from collections import defaultdict
 from enum import Enum
-from typing import TypeVar, Generic, Iterable, Union, Any, Iterator
+from typing import TypeVar, Generic, Iterable, Union, Any, Iterator, Callable
 
 from dexorder import NARG, DELETE, UNLOAD
 from dexorder.base.fork import current_fork
@@ -23,7 +22,6 @@ class DataType(Enum):
 
 class BlockData:
     registry: dict[Any,'BlockData'] = {} # series name and instance
-    adapters: dict[list['BlockDataAdapter']] = defaultdict(list)
 
     def __init__(self, data_type: DataType, series: Any, *,
                  series2str=None, series2key=None, # defaults to key2str and str2key
@@ -136,6 +134,17 @@ class BlockDict(Generic[K,V], BlockData):
     def get(self, item: K, default: V = None) -> V:
         return self.getitem(item, default)
 
+    def modify(self, item: K, func: Callable[[V],V], default: V=NARG) -> V:
+        try:
+            result = func(self.getitem(item, default))
+        except KeyError:
+            result = func(NARG)
+        self.setitem(item, result)
+        return result
+
+    def add(self, item: K, value: Union[V], default: V = 0) -> Union[V,DELETE]:
+        return self.modify(item, lambda v: v+value, default=default)
+
 
 class SeriesCollection:
     def __init__(self, series_or_datavars: Iterable[Union[Any,BlockData]]):