New Post: How to get value of reference??

Hi!

I'm reading data from an Excel sheet, that contains references. For example in Excel the Cell C4 contains "='E-Modul'!D87".
When I try to read the value of Cell C4 with ClosedXML, I need to get cell.CachedValue.
Sometimes cell.CachedValue is NULL. I got no idea what influences that... When cell.CachedValue is null, I try to get cell.Value, but that throws an Exception "Circular Reference".

The cell D87 in sheet "E-Modul" contains a formula: "=IF($B$2=1;P10;IF($B$2=2;P29;IF($B$2=3;Y48;IF($B$2=4;J67;"Ebene wählen"))))"

What am I doing wrong?

Thanks!