DIEFFECT effect;
DICONSTANTFORCE constant;
constant.lMagnitude = 10000;

ZeroMemory(&effect, sizeof(DIEFFECT));

DWORD      dwAxes = DIJOFS_Z;
LONG       lDirection = 0;

effect.dwSize = sizeof(DIEFFECT);
effect.dwFlags = DIEFF_CARTESIAN | DIEFF_OBJECTOFFSETS;
effect.dwDuration = 2*DI_SECONDS;

effect.dwSamplePeriod = 0;
effect.dwGain = 10000;
effect.dwTriggerButton = DIEB_NOTRIGGER;
effect.dwTriggerRepeatInterval = 0;      
effect.cAxes = 1; 
effect.rgdwAxes = &dwAxes 
effect.rglDirection = &lDirection 
effect.lpEnvelope = NULL; 
effect.cbTypeSpecificParams = sizeof(DICONSTANTFORCE);
effect.lpvTypeSpecificParams = &constant
effect.dwStartDelay = 0;

// create effect
HRESULT hr = _joystick->CreateEffect(GUID_ConstantForce,
	                             &effect,
			             &_effect, // var. to store effect
				     NULL);