|Here is the problem as I see it. Maybe if I explain what I'm thinking, someone else can come up with a different method.|
There are 2 ways that I know of to bold specific characters within a cell:
1 - Within Excel, select the cell, select the specific characters in the formula bar and click the Bold icon.
2 - Using the VBA Characters method.
This code will bold the Wayne in A1, after placing the string "___Hello Wayne how are you?" in the cell.
.Value = "___Hello Wayne how are you?"
.Characters(10, 5).Font.Bold = True
The problem with both of these methods is that "Wayne" really isn't in the cell when you use the Concatenation function. Instead, you have a reference to C5.
You can't select Wayne from within Excel since it will not appear in the formula bar when you select the cell.
You cannot specific the Character location for Wayne within VBA since the cell contains a formula, not a text string.
The only way I can think of to accomplish your goal is to use VBA to replace the formula with the actual string and then use the Characters method.
Let's say your Concatenation formula is in A1.
This code will replace the formula with the string and bold the portion that matches what is in C5. Keep in mind that once you run this code, the formula will be gone and changing C5 will have no impact on A1.
I suggest you try this in a backup copy of your spreadsheet. In the meantime, I'll keep looking for a way to do this without replacing the formula.
'Replace the formula with the full string
Range("A1") = Range("A1").Value
'Find the starting position of the string in C5
'within the string produced by the formula
myPos = InStr(1, Range("A1"), Range("C5"), 1)
'Bold the string from C5
Range("A1").Characters(myPos, Len(Range("C5"))).Font.Bold = True