Change 3 Dropdown Values Through Javascript

i am using below script, need to change the value of 3 dropdown on the basis of first two, Currently it showing the same value to if i am changing the values in first dropdown. Her

Solution 1:

Here is a function that you can use as an onchange event:

HTML (notice the onchange event):

<select name="sp" id="sp"class="servicecategory" onChange="change_select_values(this.value)">

JS:

function change_select_values(val){
    varsel= document.getElementById('Word_Count');
    switch(val){
        case"Medical and Biomedical Manuscript Rewriting":
            sel.options.length = 0; // clear select options
            sel.options[0] = newOption('TEXT', 'VALUE');
            sel.options[1] = newOption('TEXT', 'VALUE');
            sel.options[2] = newOption('TEXT', 'VALUE');
            sel.options[3] = newOption('TEXT', 'VALUE');
            break;
        default:        
            sel.options.length = 0;
            sel.options[0] = newOption('1 - 1000 words', 'Lessthan1000');
            sel.options[1] = newOption('1001 - 2000 words', 'Lessthan2000');
            sel.options[2] = newOption('2001 - 4000 words', 'Lessthan4000');
            sel.options[3] = newOption('4001 - 6000 words', 'Lessthan6000');
    }
    changeprice(sel.options[0].value); // change input value
}