You can accommodate the used of mixed upper/lower case by editing the first «MyField» in each expression. For example, with:
{IF«MyField»= "WELL*" «MyField» \* Charformat}
select the first «MyField» and press Shift-F9 to expose the field code. The field will now look like:
{IF{MERGEFIELD MyField}= "WELL*" «MyField» \* Charformat}
or:
{IF{MERGEFIELD MyField \* MERGEFORMAT}= "WELL*" «MyField» \* Charformat}
Edit the field code so you get:
{IF{MERGEFIELD MyField \* Upper}= "WELL*" «MyField» \* Charformat}
Press F9 when you're done. This will convert the first «MyField»'s output to all upper-case for testing purposes.
Having edited that field, you can copy/paste it over the first «MyField» in each of the remaining expressions