go to backend catalog->product->selectyourproduct->design->custom layout update and write below code .

<reference  name="product.info">
   <action method="setTemplate">yourTemplatePath/yourTemplate.phtml</action>
</reference>

or go to your theme local.xml or catalog.xml and write below code

 <PRODUCT_TYPE_grouped translate="label" module="catalog">  
     <reference  name="product.info">
         <action method="setTemplate">yourTemplatePath/yourTemplate.phtml</action>
     </reference>
 </PRODUCT_TYPE_grouped>

go to backend catalog->product->selectyourproduct->design->custom layout update and write below code .

<reference  name="product.info">
   <action method="setTemplate"><template>yourTemplatePath/yourTemplate.phtml</template></action>
</reference>

or go to your theme local.xml or catalog.xml and write below code

 <PRODUCT_TYPE_grouped translate="label" module="catalog">  
     <reference  name="product.info">
         <action method="setTemplate"><template>yourTemplatePath/yourTemplate.phtml</template></action>
     </reference>
 </PRODUCT_TYPE_grouped>

go to backend catalog->product->selectyourproduct->design->custom layout update and write below code .

<reference  name="product.info">
   <action method="setTemplate">yourTemplatePath/yourTemplate.phtml</action>
</reference>

go to backend catalog->product->selectyourproduct->design->custom layout update and write below code .

<reference  name="product.info">
   <action method="setTemplate">yourTemplatePath/yourTemplate.phtml</action>
</reference>

or go to your theme local.xml or catalog.xml and write below code

 <PRODUCT_TYPE_grouped translate="label" module="catalog">  
     <reference  name="product.info">
         <action method="setTemplate">yourTemplatePath/yourTemplate.phtml</action>
     </reference>
 </PRODUCT_TYPE_grouped>