Update query doesn't like value formatted for a different region.

[bushwacka666]

Okay, quick status update: things are looking good! Carried out additional testing, different examples, different amounts, records in both Sterling and Euro currencies, using both UK and Italian region settings... haven't ran into any other issues.

My sincerest thanks to MajP and Josef. P for together providing the final solution, and of course everybody else for kindly offering their own suggestions and assistance. Nice to know there are some people in the world who know what they're doing!

@Josef P. One additional question if I may: I'm just curious about the Dim dblODHaulageRate As Double part of the code I've implemented as per your earlier example. I've personally not come across the "Double" data type before and, to be honest, even after stepping through and testing this code I'm still not really sure I understand the significance of it. I mean, it clearly works so all good, but just for my own curiosity, what purpose is this part actually serving?

 

[Josef P.]

Double is used in the example to show that the value is a decimal number (a floating point number, to be precise).
All data types other than string must be converted to a string when concatenating a string.
If this conversion is not explicitly specified, it is (unfortunately) implicit in VBA.

An overview of data types in VBA:

Data type summary

Office VBA reference topic

learn.microsoft.com