You are talking about different QV applications, right?
You just need to provide the reload times to the MainDash application. There might be several solutions to this, you can use Rob's file age monitor as one example to learn how to do this:
I haven't seen that FileAgeMonitor app seems really interesting. Another option would be to store the reload time as field with an autogenerate statement (In the ODBC and SAP Extractor_Dash) and then load it in the MainDash as an island table:
example for ODBC and SAP extractor_Dash:
LOAD ReloadTime() as ReloadTimeODBC
store TABLE_NAME into ReloadTime.qvd(qvd);
then in the MainDash you load these qvds with the previously generated tables.
This way, you can show Reload times for any other app you need.
Another option would be like the previous comment says, to pass the reload time through a variable and then use a $(Include =) statement so the variable generated in a different document can be present in the actual one.