You would need to use SSJS to use the REST API. Something like the below would get you there:
//Sample of Str to be passed to do simple query on CB
var clientId = '12345-abcdef';
var clientSecret = '12345-abcdef';
var subDomain = 'w3443234-324dwewwer';
var mid = 123456
var queryStr = '?$filter=name eq {{assetName}}'
var authToken = generateToken(clientId,clientSecret,subDomain,mid)
var asset = getCBAsset(subDomain,queryStr,authToken)
var modifiedDate = asset.items[0].modifiedDate;
function getCBAsset(subDomain,queryStr,authToken) {
var url = 'https://' + subDomain + '.rest.marketingcloudapis.com/asset/v1/content/assets'
var contentType = 'application/json'
var result;
try {
result = HTTP.Get(deUrl, ["Authorization"], [authToken]);
} catch(e) {
result = e;
}
return result;
}
function generateToken(clientId,clientSecret,subDomain,mid) {
var authJSON = {
"grant_type": "client_credentials",
"client_id": clientId,
"client_secret": clientSecret,
"account_id": mid
}
var authUrl = 'https://' + subDomain + '.auth.marketingcloudapis.com/v2/token';
var contentType = 'application/json';
var authPayload = Platform.Function.Stringify(authJSON);
var accessTokenResult = HTTP.Post(authUrl, contentType, authPayload);
var response = accessTokenResult["Response"][0];
var accessToken = Platform.Function.ParseJSON(response).access_token;
return accessToken;
}
I haven't explicitly run the above, but it should get you where you need to be.