Excel: Worksheet.Calculate causes UDF to run infinitely

I have written a udf returns an array that is inserted at the cell location.the udf can be long running as it reaches out to a rest service to fetch data from a database. so i added a button on my ribbon to do that.

Sub ReCalc(ribbon As IRibbonControl)    Dim ws As Worksheet    ActiveWorkbook.ForceFullCalculation = True    For Each ws In ActiveWorkbook.Worksheets        ws.Calculate    Next    ActiveWorkbook.ForceFullCalculation = FalseEnd Sub

Without the ActiveWorkbook.ForceFullCalculation, worksheet.calculate does not cause the udf to run.If i simply do Application.CalculateFull, it runs the UDF - but ofcourse will also recalculate other workbooks. WHY does this work and above doesnt?

Before the UDF is called, i call this function to turn off automatic calcs and a few other things:

Sub BattenTheHatches(on_off As Boolean, Optional msg As String = "")    Application.EnableEvents = Not on_off    Application.DisplayAlerts = Not on_off    If on_off Then        Application.Calculation = xlCalculationManual        Application.Cursor = xlWait    Else        Application.Calculation = xlCalculationAutomatic        Application.Cursor = xlDefault    End If'Application.Volatile Not on_off    Application.ScreenUpdating = Not on_offEnd Sub

Any help in debugging and resolving this issue would be appreciated.