>Is there any way to update a dbase IV .MDX file inside VFP without to have to run again dbase IV and reindexing it?
From VFP help as is :
"Visual FoxPro uses a different indexing algorithm than dBASE, so if the table being converted has an associated dBASE .MDX or .NDX index, Visual FoxPro automatically creates a Visual FoxPro .CDX or .IDX index for the table.

To use a dBASE IV table with an index and without a memo field in dBASE after Visual FoxPro has converted it, open the file in dBASE and reindex. This step is necessary only if you have changed any of the data."

If you need to use in both dBase and VFP then instead of converting it to VFP use a view.
Cetin