Getting a warning then I attach strings to sheetname - Does someone have an advice?

[ande216d]

[Marcel_Rijsmus]

My advice would be,
check if your Sheet name in Excel is Sheet1 and not Sheet1 in another language
When i create an excel sheelt in my localized version of excel, it is called Blad1

[ande216d]

Thought I had checked that already but you are right! Thanks alot!