Need to fill three customer exit variables based on a manual entry variable

Hi Guys,

I have the following scenario.

I need to create 4 variables, 1 variable is user entry variable and remaining 3 variables are customer exits.

The data flow should be user can enter 1st variable, the remaning 3 fields will be filled automatically by using customer exit program. For ex:

Variable 1 = YTD Act vs. YTD LY (manual entry) then

Variable 2 = Current year (Customer exit)

Variable 3 = 100 (Customer exit)

Variable 4 = Current year - 1 (Customer exit)

I need the sample customer exit code for the above scenario. Any help would be appreciated greatly

Regards,

Navin Achanta