Using Regex in C# to check for optional comma seperated repeating sequence

Thanks in advance to all help on this.

I am rather new to regex and I am finding it a little difficult to master.

I have a WindowsForm C# in which the user can enter a set of data in a comma separated format as a single string. The data is also grouped using brackets ().

Each group consists of

(int type, int year, int age_start, int age_end)

In the text box the user can enter multiple groups

(group1),(group2)

I have managed to get the regex for splitting the groups

Regex RejectStringRegex = new Regex(@"\(([^)]*)\)");

and to split the data in the groups (I just have realised this might not account for spaces in the text)

Regex SubRejectStringRegex = new Regex(@"(\d+),(\d+),(\d+),(\d+)");

What I can't get right is how to reject malformed group strings for example

(1,89,10,10),(

or

(1,14,10,10),(2,15,20,30),(10

The code to perform the check currently looks like this. Note that I separated the regex checks as I am using them to process the data later into a List<> however if it is simpler to do it as one process then I am fine with this as well.

private bool CheckForValidReject()
{
    bool StringValid = false;
    Regex RejectStringRegex = new Regex(@"\(([^)]*)\)");
    Regex SubRejectStringRegex = new Regex(@"(\d+),(\d+),(\d+),(\d+)");

    MatchCollection AllMatches = RejectStringRegex.Matches(tbRejectString.Text);

    if (AllMatches.Count > 0)
    {
        StringValid = true;
        foreach (Match SomeMatch in AllMatches)
        {
            Match RejectMatch = SubRejectStringRegex.Match(SomeMatch.Groups[0].Value);

            if (!RejectMatch.Success)
            {
                StringValid = false;
            }
        }
    }
    return StringValid;
}

N.B: the text box is checked for empty string before calling.