How to use a web service task component

Hi,

I am using a web service task component.Here i need to pass some input and in output i will be get an URL.But here problem is  as input i have some dynamic variables and also some static variables.While i am clicking on the value field it is showing me another form where it is asking me to pass values for 5 or 6 fields,where two fileds  are dynamic.here in the value filed i cant pass a variable,so while i am checking the variable field it is asking me to pass only one variable.So problem is how to pass the values for two fields from two variables of one function.I have attached two images for your reference.

Please tell me the solution.