Integrating other website's form into mine

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>

Code (markup):

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>  

Code (markup):

 

Are you proposing that the users of your site log into the SMS site using their own log ins or that all SMS's are sent via your log in for the SMS site?

If it is the later then it will be harder depending on what security measures they have set up on the portal. Are you intending to be overt about this project with the SMS provider or are you wanting them not to know what your doing?

 

I just want to login from my site on their site and stay on my site. After that send SMS using my website, but with their form on my website

 

it is for my own usage

 

It neeeds aN API for the ineteraction between two servers..if you wish we can make it

 

can this be done with ajax?

 

The API would have to sit on the SMS providers website not yours so not something you can force them to do, if they don't have one already.

If they have one, or are willing to build one, then life is simple. It can probably be done with screen scraping depending on the security they have on their site.

There is little that can;t be done with Ajax but if it is only for yourself to use I am not sure why you'd explicitly want ajax