I found the solution:

I wrote a Table Level Script in the table SolutionsProgress.

Here is my code:

function InsertRecord()

{

}

function PostInsertRecord()

{

var currentSolutionId = CRM.GetContextInfo("Solutions","Soln_SolutionId");

if(currentSolutionId != null)

{

var currentSolutionProgress = CRM.FindRecord("SolutionsProgress",WhereClause);

var newTrackingNote = currentSolutionProgress.Soln_ProgressNote;

// if newTrackingNote is undefined (is empty), clear the field soln_lastnote.

if (newTrackingNote == null)

{

var updateSql = "UPDATE Solutions SET soln_lastnote = '' WHERE Soln_SolutionId = '"+currentSolutionId+"'";

CRM.ExecSql(updateSql);

}

else

{

var updateSql = "UPDATE Solutions SET soln_lastnote = '"+newTrackingNote+"' WHERE Soln_SolutionId = '"+currentSolutionId+"'";

CRM.ExecSql(updateSql);

}

//ErrorStr = "newTrackingNote = currentSolutionProgress.Soln_ProgressNote = ("+newTrackingNote+"), soln_lastnote updated.";

}

}

function UpdateRecord()

{

}

function DeleteRecord()

{

}