RTD - zeros returned instead of correct data

[Programmer's End Zone]

I have Excel workbooks that connect to a RTD server but this is done using
User Define Functions (UDF) to wrap up the RTD formula so it's easier for
users. I routinely get a problem when zeros are returned via the UDF when I
know valid data exists. I can prove this by simply re-entering (clicking in
the 'formula bar' and hitting 'return') the UDF formula which will then
return the correct values. Sometimes I can switch from one sheet in a
workbook that is working completely fine to another sheet that displays zeros
for all cells containing the UDF. Once again if I re-enter the UDF formula
or copy/paste an input paramenter cell for the UDFs all of the correct values
get returned. Has anyone run into this problem and solved it? My sheets can
have a lot of cells containing the UDF formula. Is it possible there is a
memory issue or a maximum limit Excel imposes on RTD or UDF updates being
called from a worksheet.

 

[Niek Otten]

Please supply the code of your UDF and the formula with which it is called.