How to enable required validation in vuelidate based on onChange event of select field - forms

Question

I have to enable required validation for the input field based on the onChange event of select field. I'm using vuelidate package for form validation in my project. Kindly provide solution to accomplish it.
My Template Code Below:
<template>
<section class="page_blk">
<form #submit="submitForm($event)" class="cryp_form">
<div class="input_ctrl_wrp">
<label for="username">Template</label>
<div class="input_select">
<select #change="getTemplate" v-model="$v.adForm.tnc.$model" name="" id="">
<option value="">Select</option>
<option value="New">New</option>
<option :value="term.idTnCTemplate"
v-for="term in termsList"
:key="term.idTnCTemplate">{{term.title}}</option>
</select>
<i class="fal fa-angle-down"></i>
</div>
</div>
<div class="input_ctrl_wrp">
<label for="username">Title</label>
<div class="input_text">
<input v-model="$v.adForm.title.$model" placeholder="" type="text">
</div>
</div>
<div class="input_ctrl_wrp">
<label for="username">Terms Of Trade</label>
<div class="input_textarea">
<textarea v-model="$v.adForm.content.$model" name="" rows="10"></textarea>
</div>
</div>
</form>
</section>
</template>
My Script Below:
<script>
import { required,requiredIf, decimal, numeric } from "vuelidate/lib/validators";
export default {
data() {
return {
adForm: {
tnc: '',
title: '',
content: '',
}
}
},
validations: {
adForm: {
tnc: {
required
},
title: {
required
},
content: {
required: requiredIf( (abc) => {
console.log('abc',abc)
return true;
})
},
schedule: {
required
}
}
},
methods: {
submitForm(e) {
},
getTemplate(e) {
}
},
mounted() {
}
}
</script>
I want to toggle the validation to required for the title and content field, if the user select new and other option from dropdown. Please provide solution to accomplish it. Thanks in advance.