report by multiple parameter with OR relationship

I am trying to create a report with three parameters (date, license number and application number). I want report by License Number or Application number in the date that I put in. I trying following in Record Selection:
1.
{Command.LICENSE_NO} = {?License Number} or
{Command.LICENSE_ID} = {?Application Number}

2.
if isnull({?License Number}) = false then
{Command.LICENSE_NO} = {?License Number};
if isnull({?Application Number})=false then
{Command.LICENSE_ID}={?Application Number};

** license_id is the application number(number). license number(string)

but both of them do not work. somehow I can not leave Application number empty.

Please Help!!!As Application Number is a number, Crystal wants you to specify one.
If you default it to 0 you could have a selection formula like

({?Application Number} = 0 and {Command.LICENSE_NO} = {?License Number})
or
({?Application Number} <> 0 and {Command.LICENSE_ID} = {?Application Number})

which means that if you supply a non-zero application number it will be used in preference to any licence id you provide.|||As Application Number is a number, Crystal wants you to specify one.
If you default it to 0 you could have a selection formula like

({?Application Number} = 0 and {Command.LICENSE_NO} = {?License Number})
or
({?Application Number} <> 0 and {Command.LICENSE_ID} = {?Application Number})

which means that if you supply a non-zero application number it will be used in preference to any licence id you provide.

I have tried using 0 as default, but for some reason. I still can not leave application number empty. I used exactly same as your code

({?Application Number} = 0 and {Command.LICENSE_NO} = {?License Number})
or
({?Application Number} <> 0 and {Command.LICENSE_ID} = {?Application Number})

but search will not start if I leave application parameter empty.

any thought?

Thanks for your help|||As Application Number is a number, Crystal wants you to specify one.
If you default it to 0 you could have a selection formula like

({?Application Number} = 0 and {Command.LICENSE_NO} = {?License Number})
or
({?Application Number} <> 0 and {Command.LICENSE_ID} = {?Application Number})

which means that if you supply a non-zero application number it will be used in preference to any licence id you provide.

Got it working with your code!!!

Thanks your so much!!