Help regarding MSI Serial Key Validation

[Exelio]

hi all,

I am using ORCA to validate the product key in C# 2005 windows application.

i am using the following C++ code in a dll to be added to the MSI for validation.

UINT __stdcall ValidateSerial(MSIHANDLE hInstall)
{
TCHAR szPidKey[PIDKEY_LENGTH];
DWORD dwLen = sizeof(szPidKey) / sizeof(szPidKey[0]);

///retrieve the text entered by the user
UINT res = MsiGetPropertyA(hInstall, _T("PIDKEY"), szPidKey, &dwLen);
if(res != ERROR_SUCCESS)
{
//fail the installation
return 1;
}

bool snIsValid = true;
//validate the text from szPidKey according to your algorithm
//put the result in snIsValid

//the template we use is <###-####> = ; # digit between 0 and 9
//the algorithm is very simple (XY * Z + 7) * 13 = ABCD / 2
int xy = DIGIT(szPidKey[0]) * 10 + DIGIT(szPidKey[1]);
int z = DIGIT(szPidKey[2]);
int left = ((xy * z + 7) * 13 ) * 2;
int right = DIGIT(szPidKey[4]);
right = right * 10 + DIGIT(szPidKey[5]);
right = right * 10 + DIGIT(szPidKey[6]);
right = right * 10 + DIGIT(szPidKey[7]);
snIsValid = (left != 0) && (right != 0) && (left == right);

TCHAR * serialValid = NULL;
if(snIsValid)
serialValid = _T("TRUE");
else
{
//eventually say something to the user
::MessageBox(0, _T("Invalid Serial Number"), _T("Message"), MB_ICONSTOP);

serialValid = _T("FALSE");
}

res = MsiSetPropertyA(hInstall, _T("SERIAL_VALIDATION"), serialValid);
if(res != ERROR_SUCCESS)
{
//fail the installation
return 1;
}

//the validation succeeded - even the serial is wrong
//if the SERIAL_VALIDATION was set to FALSE the installation will not continue
return 0;
}

but when i execute the above code, i am getting the following error.
error LNK2019: unresolved external symbol _MsiSetPropertyA@12 referenced in function "unsigned int __stdcall ValidateSerial(unsigned long)" (?ValidateSerial@@YGIK@Z) CustomAction.obj

i have included and

I am a beginner in VC++ and could anybody help me with some suggestions
Thanks in advance.

Regards

exelio