Passing value to saved data binding from input field

I created a new data binding using flicker web service. I can see following code in data binding code

{"text":"mac","tags":"","tag_mode":"any","group_id":"","radius":"","lat":"","lon":"","per_page":"10","page":"10"}

I wish to pass variables here that i will get from input, is there a way to pass custom variable from text input field?

So it should be something like this

{"text":"{custom_value}","tags":"","tag_mode":"any","group_id":"","radius":"","lat":"","lon":"","per_page":"{custom_number}","page":"10"}

Any help would be appreciated.

thanks