Using shared variables in Crystal report

1. Create a formula in mainreport as @iammainformula with shared variable declared as Shared stringVar amtword := {?amntInWords};

2. Create a formula in subreport as @iamsubformaula with the shared variable with same name as we declared in the main report
Shared stringVar amtword ;
amtword;

now we can access the value from the main report in the sub report