Correct. The API def for DELETEBUTTON specifies an Index whereas Command Identifier is presumably the idCommand field of TBBUTTON. The API docs are different for each function. Having tested this using the idCommand field of TBUTTON, rather than the Index, it works. Problem solved. Many thanks.

Will5801 wrote: // WHAT EXACTLY IS THE STORAGE TYPE FOR THIS int ? That's a native int on the CRT heap. Will5801 wrote: // PRESUMABLY ON THE UNMANAGED HEAP, BUT HOW CAN THIS HAPPEN FOR INT? // DOESN'T INT ALWAYS MAP TO System.Int32? You're using int in the native context (*, new) so the compiler can infer what int to use....the native one in this case. Mark Salsbery Microsoft MVP - Visual C++ :java:

but in C#: byte[] b; creates an instance for system.array

I have two versions of SENS.DLL both version 5.2.3790.3959 According to WinMerge they are binary identical. However, they are different sizes on disk? C:\windows\system32\sens.dll (65,024 bytes) C:\windows\sysWOW64\sens.dll (37,376 bytes) I also loaded them both into TextPad and they appear identical, both have length of 37,376 Why they appear different sizes on disk? It appears that MS has accidentally released a 32 bit build of the DLL for both 32 bit and 64 bit use?