diff --git a/sysdata_windows.go b/sysdata_windows.go
index 714f501..acc7070 100644
--- a/sysdata_windows.go
+++ b/sysdata_windows.go
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"syscall"
 	"unsafe"
+	"sync"
 )
 
 type sysData struct {
@@ -19,6 +20,7 @@ type classData struct {
 	name	string
 	style		uint32
 	xstyle	uint32
+	mkid		bool
 }
 
 //const controlstyle = _WS_CHILD | _WS_VISIBLE | _WS_TABSTOP
@@ -34,13 +36,29 @@ var classTypes = [nctypes]*classData{
 //		name:	"BUTTON"
 //		style:	_BS_PUSHBUTTON | controlstyle,
 //		xstyle:	0 | controlxstyle,
+//		mkid:	true,
 //	},
 }
 
+var (
+	cid _HMENU = 0
+	cidLock sys.Mutex
+)
+
+func nextID() _HMENU {
+	cidLock.Lock()
+	defer cidLock.Unlock()
+	cid++
+	return cid
+}
+
 func (s *sysData) make() (err error) {
 	ret := make(chan uiret)
 	defer close(ret)
 	ct := classTypes[s.ctype]
+	if ct.mkid {
+		s.cid = nextID()
+	}
 	uitask <- &uimsg{
 		call:		_createWindowEx,	
 		p:		[]uintptr{
@@ -65,7 +83,9 @@ func (s *sysData) make() (err error) {
 	}
 	s.hwnd = _HWND(r.ret)
 	addSysData(s.hwnd, s)
-	// TODO parent
+	if ct.mkid {
+		addSysDataID(s.cid, s)
+	}
 	return nil
 }
 
diff --git a/sysdatacache_windows.go b/sysdatacache_windows.go
index 620d6ac..16848e2 100644
--- a/sysdatacache_windows.go
+++ b/sysdatacache_windows.go
@@ -8,51 +8,39 @@ import (
 
 // I need a way to get a sysData for a given HWND or a given HWND/control ID. So, this.
 
-type sdcEntry struct {
-	s			*sysData
-	members		map[_HMENU]*sysData
-}
-
 var (
 	sysDatas = map[_HWND]*sdcEntry{}
 	sysDatasLock sync.Mutex
+	sysDataIDs = map[_HMENU]*sdcEntry{}
+	sysDataIDsLock sync.Mutex
 )
 
 func addSysData(hwnd _HWND, s *sysData) {
 	sysDatasLock.Lock()
 	defer sysDatasLock.Unlock()
-	sysDatas[hwnd] = &sdcEntry{
-		s:			s,
-		members:		map[_HMENU]*sysData{},
-	}
+	sysDatas[hwnd] = s
 }
 
-func addIDSysData(hwnd _HWND, id _HMENU, s *sysData) {
-	sysDatasLock.Lock()
-	defer sysDatasLock.Unlock()
-	if ss, ok := sysDatas[hwnd]; ok {
-		ss.members[id] = s
-	}
-	panic(fmt.Sprintf("adding ID %d to nonexistent HWND %d\n", id, hwnd))
+func addIDSysData(id _HMENU, s *sysData) {
+	sysDataIDsLock.Lock()
+	defer sysDataIDsLock.Unlock()
+	sysDataIDs[id] = s
 }
 
 func getSysData(hwnd _HWND) *sysData {
 	sysDatasLock.Lock()
 	defer sysDatasLock.Unlock()
 	if ss, ok := sysDatas[hwnd]; ok {
-		return ss.s
+		return ss
 	}
 	return nil
 }
 
-func getIDSysData(hwnd _HWND, id _HMENU) *sysData {
-	sysDatasLock.Lock()
-	defer sysDatasLock.Unlock()
-	if ss, ok := sysDatas[hwnd]; ok {
-		if xx, ok := ss.members[id]; ok {
-			return xx
-		}
-		panic(fmt.Sprintf("getting nonexistent ID %d for HWND %d\n", id, hwnd))
+func getIDSysData(id _HMENU) *sysData {
+	sysDataIDsLock.Lock()
+	defer sysDataIDsLock.Unlock()
+	if ss, ok := sysDataIDs[id]; ok {
+		return ss
 	}
-	panic(fmt.Sprintf("getting nonexistent HWND %d\n", hwnd))
+	panic(fmt.Sprintf("getting nonexistent ID %d for HWND %d\n", id, hwnd))
 }