Store value in UDF

Sir,

I want to store value using calling a function on a event please correct my function steps how to store a value in UDF

[System: UDF]
DelVchUserName : String: 50301 ; storage at the time of voucher entry
DelVchBody : String: 50302

[Function:MyFun]
03a: Set Target: DelVchUserName
04: Set: DelVchUserName : "AA"
04a: Set Target: DelVchBody
05: Set: DelVchBody : " XYZ....ETC"
06: Save Target

Thanks and regards

 

when do u want to call this function

 

thanks done

 

can someone correct this ;

[Field:Refnobb]
Use :Name Field
Set As : if $$IsVoucher then if $IsSalesVch then $field1 else + $field2
Width : 18
Align:right
Style : Normal
Border: Thin Left