Read Table onBlur of Inputfield

Hi,

I have a inputfield say: t_comp_code where I want the user to enter the Company Code.Then I want to check the Company Code master table to see if the entry exists or not. This I want to do oBlur of the field and then output an error message in an alert box via Javascript.

How do I achieve reading an internal table & then calling the Javascript function if sy-subrc = 0?

And where do I select all values of the master table?

As I am new to BSP I am having problems visualizing this.

Please help.

Regards

Tejaswini