Extract column index from Excel cell index, works for AA, AAA etc

Hi, how do I extract the column index from Excel cell index?

Should work for cells A-Z, AA, AB, CA, AAB etc

input: Excel cell index e.g. CA11, ACA20

output: column index CA, ACA

@DEATHFISH

Try below expression:

System.Text.RegularExpressions.Regex.Replace(yourString,"[\d-]",String.empty)