Multiple Input Problem

This is what I need - is it possible?

I have four computers. All run the same excel spreadsheet with one line input of customer names addresses etc. I need them to see in real time the next line to fill in eg if computer one is filling line say 10, computer two needs to see this and therefore fills out the next available line line 11. The same with computer three seeing line 12 is available. The whole completing the master sheet on computer four which will visually show all lines of information. The reason for this is the need to have one master sheet being compiled from customer telephone calls needed to be data recorded from three telephone lines.

I have had some excellent help advising the mapping of computers and sharing of worksheets, however the minimum update time I can see is every 5mins. I need to see in real time - is there any soloution?

Thank you very much for taking time to read this.

or perhaps an access data base instead ?