special tags

I have this problem now.
I have this xml messagge

           <parameters>
                <family-name>Rossi</family-name>
                <first-name>Paolo</first-name>
                <cod-fisc>123123123</cod-fisc>
	      <home-address>via Vai</home-address>
	      <cell-phone>12354356</cell-phone>
	      <e-mail> pippo@yrr.it.net</e-mail>
            </parameters>            
 The problem is that family-name, first-name, cod-fisc and home-address are mandatory and I need at least one of cell-phone
 or e-mail, so I could have these 3 kind of messages:
          <parameters>
                <family-name>Rossi</family-name>
                <first-name>Paolo</first-name>
                <cod-fisc>123123123</cod-fisc>
	      <home-address>via Vai</home-address>
	      <cell-phone>12354356</cell-phone>
	      <e-mail> pippo@yrr.it.net</e-mail>
            </parameters>

          <parameters>
                <family-name>Rossi</family-name>
                <first-name>Paolo</first-name>
                <cod-fisc>123123123</cod-fisc>
	      <home-address>via Vai</home-address>
	      <cell-phone>12354356</cell-phone>

            </parameters>

          <parameters>
                <family-name>Rossi</family-name>
                <first-name>Paolo</first-name>
                <cod-fisc>123123123</cod-fisc>
	      <home-address>via Vai</home-address>

	      <e-mail> pippo@yrr.it.net</e-mail>
            </parameters>

There is some way to do this with XSD?
Thank you very much for your help
Debora Vanni