String pattern search and replace in C#

I used two separate dictionaries to associate the source and column fields, as I thought the associations are between source and column fields only. The sample code is made for a button that replaces the text of a label when it is clicked, but it can be adapted to any similar situation. So far this is what I came up with:

using System;
using System.Collections.Generic;
using System.Text;
using System.Text.RegularExpressions;
using System.Windows.Forms;

namespace RegexTest
{

public partial class Form1 : Form
{
    Dictionary<string, string> values = new Dictionary<string, string>();
    Dictionary<string, string> columns = new Dictionary<string, string>();
    public Form1()
    {
        InitializeComponent();
        InitValues();
    }

    private void InitValues()
    {
        values.Add("Source1", "ABC");
        values.Add("Source2", "DEF");
        values.Add("Source3", "GHI");

        columns.Add("Column1", "Col1");
        columns.Add("Column2", "Col2");
        columns.Add("Column3", "Col3");
    }

    private void button1_Click(object sender, EventArgs e)
    {

        // Create the pattern
        string pattern = "[a-z1-9]+\\[Source[0-9]+\\]\\.\\[[a-z1-9]+:Column[0-9]+:[a-z1-9]+\\][a-z1-9]+";
        // Create a Regex  
        Regex rg = new Regex(pattern);
        // Get all matches  
        MatchCollection matchedValues = rg.Matches(label1.Text);

        StringBuilder sb = new StringBuilder();
        // Replace all matches 
        for (int count = 0; count < matchedValues.Count; count++)
        {          
            //copy the anytext part until the source
            sb.Append(matchedValues[count].Value.Substring(0, matchedValues[count].Value.IndexOf('[')));
            //replace the Source parts
            sb.Append(values[matchedValues[count].Value.Substring(matchedValues[count].Value.IndexOf('[') + 1,
                matchedValues[count].Value.IndexOf(']') - matchedValues[count].Value.IndexOf('['))]);
            //now copy in the same way the anytext after source
            //split in the same way around the : and use the columns dictionary

            //finally, replace the original string with the value from string builder
            label1.Text = sb.ToString();
            sb.Clear();
        }
    }
}
}

The other parts are done in a similar way (I only made it find the first part, the "source", for the column part it is the same). If you'll need further help please ask and I'll answer as soon as possible. I also assumed that the anytext parts can contain only alpha-numerical text, if other characters can be found there, I'll edit the regex pattern.

Just posting the final code that I got it working with the approach suggested by @Youssef13

Dictionary<Tuple<string, string>,Tuple<string,string>> sourcecolumncodeandvalue = new Dictionary<Tuple<string, string>, Tuple<string, string>>();
            sourcecolumncodeandvalue.Add(Tuple.Create("Source1", "Column1"), Tuple.Create("ABC", "Col1"));
            sourcecolumncodeandvalue.Add(Tuple.Create("Source2", "Column2"), Tuple.Create("DEF", "Col2"));

            Dictionary<string, string> codeandvaluereplacementlist = new Dictionary<string, string>();

            var pattern = @"\[(.*?)\]\.\[(.*?)\]";
            var filetext = "anytext[Source1].[anytext:Column1:anytext]anytext anytext[Source2].[anytext:Column2:anytext]anytext";
            var matchesfound = System.Text.RegularExpressions.Regex.Matches(filetext, pattern); //find the pattern [].[]
            foreach (System.Text.RegularExpressions.Match  m in matchesfound)
            {
                string datasource = string.Empty;
                string columnname = string.Empty;
                string replacementtext = string.Empty;

                string[] sourceandcolumnsplit = m.Value.ToString().Split('.');//split [].[] into two based on '.' character
                datasource = sourceandcolumnsplit[0].Replace("[","").Replace("]",""); //remove square brackets               
                //Column value is in between ':' character (ex: anytext:Column2:anytext)  so split it further 
                string[] columnsplit = sourceandcolumnsplit[1].Split(':');
                columnname = columnsplit[1];
                //We got the source and column codes, now get corresponding values from the dictionary
                Tuple<string,string> sourceandcolumnvalues;
                sourcecolumncodeandvalue.TryGetValue(Tuple.Create(datasource, columnname),out sourceandcolumnvalues);

                //construct the replacement value string for each code string
                codeandvaluereplacementlist.Add(m.Value.ToString(), "[" + sourceandcolumnvalues.Item1 + "]." + columnsplit[0] + ":" + sourceandcolumnvalues.Item2 + ":" + columnsplit[2]);
            }
            //Finally loop through all code matches and replace with values in the file text
            foreach (var codeandvalue in codeandvaluereplacementlist)
            {
                filetext = filetext.Replace(codeandvalue.Key, codeandvalue.Value);
            }

var source = "anytext[Source1].[anytext:Column1:anytext]anytext";
var src1 = "Source1";
var dest1 = "ABC";
var src2 = "Column1";
var dest2 = "Col1";

var result = source
                .Replace("[" + src1 + "]", "[" + dest1 +"]")
                .Replace(":" + src2 + ":", ":" + dest2 +":");

https://dotnetfiddle.net/5cRnYD

Of course you may use any list/dictionary/file for src and dest values.