Hide the cursor using User32.dll

Hi there,
I am trying to hide/show the cursor using User32.dll.
My OS is Windows 10 Pro x64.

I use this script to hide the cursor:
DLL.CallFunction(_SystemFolder.."\\User32.dll", "ShowCursor", "0", DLL_RETURN_TYPE_INTEGER, DLL_CALL_CDECL);

And this one to show it:
DLL.CallFunction(_SystemFolder.."\\User32.dll", "ShowCursor", "1", DLL_RETURN_TYPE_INTEGER, DLL_CALL_CDECL);

But my app crashes executing these scripts.
What could be the reason?