I am thinking of using WinWedge to set up a control loop. Data will be collected via the RS232 port into Excel & then data will be taken from Excel & sent back to the RS232 port. Is this possible ?

This is exactly what WinWedge is designed to do. Data and commands can be sent directly from Excel to WinWedge to transmit out to your serial devices. Hence you can have Excel use WinWedge to control devices.

WinWedge is controlled from Excel by sending DDE commands to it.

The following Excel VBA subroutine sends a string of control codes out the serial port by issuing the DDE command "[SendOut()]" to WinWedge. This example sends an escape character (ASCII 27), a capital "P" and a carriage
return-linefeed (ASCII 13 and ASCII 10).

Sub SendEscapeP()
ChannelNumber = Application.DDEInitiate("WinWedge", "COM1")
Application.DDEExecute ChannelNumber, "[SENDOUT(27,'P',13,10)]"
Application.DDETerminate ChannelNumber
End Sub

This is just one Example of data being sent from Excel via WinWedge to a serial device. Any data, commands or variables can be sent out.