Strange problem with F4 help

Hello All,

I have created a F4 help for one field.

In my program i have used this field for parameters statement.

Here is the problem:

when i run the program i can see the value when i press F4 but when i do some actions and if i come back the same screen F4 is not working.

Can any one tell me what is the problem with F4.

Regards,

Lisa