Shared Spreadsheet - Collect Information Through VB

I have a spreadsheet here that collect information through vb, now when the first agent is done with the information needed and click on the save command button the information is saved in the spreadsheet.

For example:

A | B | C | D | E
1 Date | Name | Birthdate | Gender | Age
2 11/20/11 | Greg White | 04/12/1977 | Male | 34
3 11/20/11 | Greg Blue | 04/12/1977 | Male | 34
4 11/20/11 | Greg Green | 04/12/1977 | Male | 34
5 11/20/11 | Greg Black | 04/12/1977 | Male | 34

Now theres no problem with this instance.... the problem arise when the second agent do the same thing..... when i check the spreadsheet the information was overwritten.

What really should be happening is that when the first agent click the save command button the spreadsheet will be saved so that when the next agent click the save button it will go to the next line.

Another thing that i noticed, since the spreadsheet is shared through the network, it takes time before the information is saved.

1. When Save button is clicked the spreadsheet will be saved.
2. A code (if there is any) to speed up the saving of shared excel file.