Restricted Remote Access

I belong to a marketing company with clients who have databases residing on their local computers. We would like to write a program, say written in visualbasic, which would reside on the client's computer, and retrieve and display very specific, limited information from their database. We need to be able to access this program from our computer. And our clients need to know that access to run this program is the only access that we have to their system.

How would this be implemented? It has been suggested to us that pcAnywhere or GoToMyPc could easily accomplish this. Is this true? How does it work? Does anyone have experience with a comparable situation? Are there alternative solutions? How could we make the client feel secure and comfortable that we are not "breaking into" their computer system, but rather only accessing this one program that we need?

Ideas for solutions would be welcome. My background is html/javascript/Server Side code, and my knowledge of networking is not extensive, so details would be helpful, as would suggestions for forums which might be more suitable for this question. Thank you.