How to convert units of input cells automatically

[haroocivil]

HI,

I HAVE DATA INPUTS IN CELLS A1 TO A5.
I WANT VALUES IN "INPUT CELL "TO CHANGE BASED ON UNIT SYSTEM (METRIC SYSTEM OR BRITISH SYSTEM) IF SELECTED AT FIRST.
it is important to consider that that values in CELL A1 TO A5 ARE "INPUTS"

FOR EXAMPLE
[TABLE="width: 477"]
<tbody>[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][TABLE="width: 477"]
<tbody>[TR]
[TD="colspan: 4"]Select Units[/TD]
[TD]Metric System [/TD]
[/TR]
[TR]
[TD]DATA INPUTS
8000 Cumecs
50 meter
300 meter
400 meter
90 meter[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
</tbody>[/TABLE]
[/TD]
[/TR]
</tbody>[/TABLE]