APEX

Hi All. Im new to Apex.

Present Approach -
I have a dynamic report region developed using API's like APEX_ITEM etc. I am using java scripts to validate these dynamic items and popup alert messages as shown below -

function ValidateNotObservedCB(p_row_num)
{
var v_row_num = p_row_num;
var v_not_observed_cb_status = document.getElementById('f_notobserved_'+v_row_num).checked;
var v_not_in_district_cb_status = document.getElementById('f_notindistrict_'+v_row_num).checked;
var v_program_code = document.getElementById("f_program_code_"+v_row_num).value;
if ( (v_program_code.length>0)&& ( document.getElementById('f_notobserved_'+v_row_num).checked==true ))
{
bold alert("You have already entered a program code.") bold
document.getElementById('f_notobserved_'+v_row_num).checked=false ;
document.getElementById('f_notobserved_'+v_row_num).value='N';
} else if ( (v_program_code.length==0)&& ( document.getElementById('f_notobserved_'+v_row_num).checked==true )) {
document.getElementById('f_notobserved_'+v_row_num).value='Y';
document.getElementById('f_notobserved_'+v_row_num).checked=true ;
} else
{
document.getElementById('f_notobserved_'+v_row_num).checked=false ;
document.getElementById('f_notindistrict_'+v_row_num).checked=false;
document.getElementById('f_notindistrict_'+v_row_num).value='N';
document.getElementById('f_notobserved_'+v_row_num).value='N';
}
}

Question/Issue - How can I convert these alert messages into Inline messages to show on the page, similar to what appears when we do Item Validations in APEX.

Waiting for responses as this is an urgent requirement.
Thanks in Advance,
Madhu