Dcom into SAP

We are currenly trying to communiate from a Com component into SAP. We have created a RFC within SAP with two parameters, a filename and table. When we call the RFC using VB via Dcom and we do not specify any paramters, it works and envokes to RFC component within SAP. However, when the VB program tries to call the RFC with parameters we get the error ‘Invalid Number of arguments’ at VB complile. The RFC within SAP has the parameters as required. Has anyone called an RFC within SAP and passed tables and fields?