Add brackets to an expression with regex - excel

Question

I want to add parentheses to parts of an expression.
The parts are any multiplied expressions that are NOT in parentheses.
For example, change:
a * b + c + d * e * f + g
to:
(a * b)+ c +( d * e * f) + g
another example, change:
(a1+b1) + ( c1 * d1) + e1 * f1 *g1 * h1 + J1
to:
(a1+b1) + ( c1 * d1) + (e1 * f1 *g1 * h1) + J1
The only elements in the expression to check will be * + ( ) and variable names with no spaces, like a1 f1 p3 etc.
I came up with something but it shows the expressions WITH brackets. I want the opposite of that.
This is what I have:
Function testParen()
Dim cText As String, cPattern As String
Dim itemFound As Variant, nItems
Dim getParen As New RegExp
getParen.Global = True
getParen.IgnoreCase = True
cText = "(a1*q1) + (b1*c1) + d1*e1*f1 * (g1+h1) + (k1*m1) "
cPattern = "(^|[^*])\(([^()]+)\)"
'cPattern = "\("
getParen.Pattern = cPattern
cText = Replace(cText, " ", "")
Dim mc As MatchCollection
Set mc = getParen.Execute(cText)
nItems = mc.Count
'Debug.Print vbNewLine
If nItems > 0 Then
Debug.Print nItems
For Each itemFound In mc
Debug.Print Replace(itemFound, "+", "")
Next
Else
Debug.Print "No items"
End If
End Function

Answer 1

I recommend you rethink your approach and parse the expression properly rather than just inserting parentheses. Perhaps initially splitting on + would be simpler, rather than using a regex that you don't fully understand and can't confidently adjust.
Anyway, here is an example in JavaScript of the kind of regex that could be used. I will leave any conversion to VBA to you.
const rx = /(\+\s*|^\s*)((?:\s*\w+\s*\*)+\s*\w+)(?=\s*\+|\s*$)/g;
const expression = '(a1+b1) + ( c1 * d1) + e1 * f1 * g1 * h1 + J1';
console.log(expression.replace(rx, '$1($2)'));
Note that the above has not been properly tested and may be brittle. I am not going to try and explain it, but you could enter the regex into for example https://regex101.com/ if you want a breakdown of how it works.
In the regex, the first \+ could be replaced with for example [^(\s\w] and the second \+ with [^)\s\w], if for example you want - to work also.