can we call a xml request from another xml request

Do you mean to say that there are two steps in a test case? And you need to retrieve some value from the previous response?
Then you need to look at the properties.
Please see if these links might be helpful:
http://www.soapui.org/Functional-Testin ... rties.html
http://groovyinsoapui.wordpress.com/tag ... eexchange/