needs to be compiled on the same DLL architecture. (32bit or 64bit)

GetFunctionFromDLL.c

#include <stdio.h>
#include <windows.h>

void *GetFunctionFromDll(LPCSTR DLL, LPCSTR procName) {
	HMODULE hModule;
	void *function;
	
	if ((hModule = LoadLibrary(DLL)) == NULL)
	{
		fwprintf(stderr, L"ERROR: could not load DLL.\n");
		return NULL;
	}
	
	if ((function = GetProcAddress(hModule, procName)) == NULL)
	{
		fwprintf(stderr, L"ERROR: could not find function.\n");
		return NULL;
	}
	
	return function;
}

/*///////////////////////////////////
	
		Testing:
		
///////////////////////////////////*/

int main(void) {
	typedef BOOL (*BLOCKINPUT)(BOOL blockIt);
	BLOCKINPUT BlockInput = GetFunctionFromDll("user32.dll", "BlockInput");
	
	BlockInput(1);
	Sleep(3000);
	BlockInput(0);
	
	while (1);
	return 0;
}