Search for field on selection-screen

Hi all,

I have requirement to create search for fields which are on seelction-screen.

i have fallowing fields on selection-screen.

Company Number,

Currency

Decimal places .

First i need to create F4 help for Company numer.( it has only five field values)

Then Based on Company Number, i need to keep default curreny there.

Based i need to keep decimal points for that on selection-screen .

Is there any point to know sample code for this.

Thanks in advance,

Regards,

Bhaskar