>>>Could it be that the function isn't visible anymore? Try to suspend the execution while grid is active and call your function in the command window (adjusting for the datasession if necessary). Check the Set("procedure"). Seems that your grid can't evaluate the controlsource because it can't find the function.
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>>The function is visible.
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>Beats me. Could be some minor syntactical error, which passes ok but leaves you with no records. AFAI remember, you said the identical UDF works OK in another grid, right? Why don't you try to just copy & paste the .controlsource expression from the other grid? Could you open the form in the class browser and copy the part of the code (in "view source code" window) where this column is defined, so we can take a look?
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>I've just checked couple of grids of mine, and I've actually used the UDFs as control sources, and it worked fine; don't know if it matters that the grids are used as read-only.
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>I've always found it a bit quirky that VFP uses eval() internally so much. So many things are put inside strings, and then you are never sure if they are taken as literals at compile time, and checked upon instantiation, or they really get checked at compile time.

Beats me too! The whole thing was pasted from a form that worked fine. No changes made. Just the data environment. (The control source was the same data file but went from being just another file in the DE to the initial selected alias) I reckon it's a timing thing internal to Fox.
Anyway it'll come good one day :-)
Dave