So, if I understand you correctly, although your report connects to 5 different XML files, you only want to show the data from one of them based on a parameter. Is that correct?
Assuming that all five tables have the same number of fields, you would create a formula for each field you want to display and another one for each group you need on the report. The formulas would be in this type of format:
Switch (
{?MyParam} = "1", {Table1.Field1},
{?MyParam} = "2", {Table2.Field1},
{?MyParam} = "3", {Table3.Field1},
{?MyParam} = "4", {Table4.Field1},
{?MyParam} = "5", {Table5.Field1},
True, "Not Found")
Use these formulas on the report instead of the actual fields.
-Dell