Parameters
A Field Parameter is a dependency created to DataBind one field of the form using the selected value from another field on the same form as a parameter that is sent in the query, enabling interconnected fields on your form. A good example of this is the country and region of the user on registration. When the user selects the country of origin, the drop down list of the regions must change to show the regions within that country. This could also be used on multi-paged forms to pass the value of one field on page one to another on page two, and so on.
Parameter Elements
Param Name
The Param Name is the name of the class of data from the source field that the parameter will be taken from. Thus from a drop down list you can have the text field or the value field of the drop down lists’ databound source.
Source Field
This setting is used to define the Source Field Name that is used as the Master Control for this dependency. This Source Field Name will control the association by passing a parameter from the selected index in that list control. This parameter value is passed to the query which then returns the result set of data for the population of the dependant field.
Column Index
The Column Index is helpful when you have several Parameters that make up the databinding of a field control. You would need to display them in sequence to make sure that they are logical and visually dependant on each other. This setting is automatically incremented.