You can't have a single unitcode that starts with (10 or CO or TH) and also starts with WE. So really what you need is starts with 10 or CO or TH or WE. This will get you records with unit codes that start with any of the four options.
Try this for a formula if you just need to identify the records:
Left({incilog.unitcode}, 2) in ["10", "CO", "TH", "WE"]
If you're using this in the Select Expert to filter the records coming into the report, you don't want to do it that way, though, because Crystal can't pass its own formulas to the database for processing and will pull ALL of the data into memory and filter it there. Instead, you'll do this in the Select Expert formula:
(
{incilog.unitcode} StartsWith "10" OR
{incilog.unitcode} StartsWith "CO" OR
{incilog.unitcode} StartsWith "TH" OR
{incilog.unitcode} StartsWith "WE"
)
Note the use of parentheses - if you have any other selection criteria, you MUST have them in order for the filter to work correctly.
-Dell