static extern UInt32 MsiApplyPatch(string patchPackage, string installPackage, INSTALLTYPE installType, string commandLine);

Declare Function MsiApplyPatch Lib "msi.dll" (TODO) As TODO

UInt32 ret = MsiApplyPatch("TestInstall.msp", "", INSTALLTYPE_DEFAULT, "REINSTALL=ALL REINSTALLMODE=omus REBOOT=Suppress");