I made the following changes, and got halfway there...

Public CharcoalText As String
Public AR_Text As String
Public GRAN_Text As String
Public FINE_Text As String




Function Charcoal_Check()
AR_Text = "AR "
GRAN_Text = "G"
FINE_Text = " F"

If AR_NU Then AR_Text = " "
If AR_P Then AR_Text = "<b>AR </b>"
If G_NU Then GRAN_Text = " "
If G_P Then GRAN_Text = "<b>G</b>"
If F_NU Then FINE_Text = " "
If F_P Then FINE_Text = "<b> F</b>"

CharcoalText = AR_Text & GRAN_Text & FINE_Text

End Function
Now, it shows correctly in my column, but the bold tags are there too.