I have done a similar thing calling an Oracle SP from VB, but too much code to put here.
It involved various calls to the ODBC.DLL library:
SQLAllocStmt
SQLPrepare
Parameter binding using: SQLBindParameterString/Double/Long/Integer
SQLExecute
Get the output parameters (if any), then tidying up with SQLFreeStmt
Try to look these up on MSDN or similar to get examples.
HTH
M.