Integrating other website's form into mine website

[dada1]

There is website in my country for sending free SMS but it is portal and it takes a long time to load.
I wanted to make site where I will integrate login and form for sending sms. How to do that, when users login to my site, actually login to that portal but stays on my site to send sms?
Just give me hints how to do that

Here is code
LOGIN BOX

<form name="asmpform" action="http://webauth.vip.hr/vasmpauth/ProcessLoginServlet">
<label for="UserID">Korisnicko ime:</label>
 
<input name="UserID" class="login_username" id="login_username" type="text" />
<br />
<label for="Password">Lozinka:</label>
<span class="r">
<input name="Password" class="login_password" id="login_password" type="password" />
<span class="btn-login0"><input type="submit" name="login_submit" class="login_submit" value="" ></span>
</span>
<input type="hidden" name="userRequestURL" value="http://www.vip.hr/">
 
<input type="hidden" name="level" value="30">
</form>

SEND SMS FORM

<form id="sendsms_form" action="http://www.vip.hr/naslovnica?p_p_id=wavetechcommunitycorner_WAR_wtcommunity&p_p_lifecycle=1&p_p_state=normal&p_p_mode=view&p_p_col_id=118_INSTANCE_g0jU_column-2&p_p_col_count=2&_wavetechcommunitycorner_WAR_wtcommunity_module_action=portal_sendSMS_submit" method="post" class="sms" name="sendsms" onSubmit="return checkFields();">
<input name="formflag" type=hidden value="true">
<input name="msisdn" type=hidden value="" id="msisdn" />
<input name="module_action_redirect" type=hidden value="/" id="" />
 
<div style="float:left; margin-right:15px;"><select name="sms_broj_operatera" class="sms_broj_operatera1" id="sms_broj_operatera">
</select></div>
<div><input type="text" name="sms_broj_mobitela" class="sms_broj_mobitela1" id="sms_broj_mobitela"/></div>
<br />
<div style="margin-right:20px;">
 
<textarea name="sms_poruka" class="sms_poruka1" rows="4" cols="20" id="sms_poruka"></textarea>
</div>
                        <br />
<div style="margin-right:20px;"><input type="text" class="sms_reklama1" name="sms_reklama" readonly value="<poslano sa Vip Web SMS www.vip.hr>" id="sms_reklama"/></div>    
 
<div class="sms-brojac-znakova"><span id="charleft"></span> znakova<span id="broj_SMSova"> / 1 poruka</span></div>
 
<input type="image" src="http://sc.vip.hr/vip_portal-theme/images/button-portlet-submit.png" class="sms submit" name="sms_submit" id="sms_submit" value="Posalji"/>
<div><input type="checkbox" name="sms_odgovor_na_mobitel" id="sms_odgovor_na_mobitel" class="sms_odgovor_na_mobitel float_left" checked="checked"/>&nbsp;&nbsp;<label for="sms_odgovor_na_mobitel" class="sms_odgovor_na_mobitel_label float_left">Odgovor na mobilni telefon</label></div>
 
<div class=" clear"><font class="bigger"><strong>14</strong></font> besplatnih poruka koje možete danas poslati</div>
</form>  
 

[NitinSawant]

you can use screen scraping to login and post data to external website

ASP.NET Screen scraping

[dada1]

I'll try that