Convert row, column to Excel range in Axapta

Convert row, column to Excel range in Axapta 
This method is show how to convert row and column to Excel range:
rowfrom = 1,
colfrom = 1,
rowto = 5,
colto = 5;
>> A1:E5

public str convertToRange(int rowfrom, int colfrom, int rowto = 0,int colto = 0)
{
    str     strrange, srange1;

    ;
    if(rowfrom <= 0 || colfrom <= 0)
    {
        throw warning("We don`t have row <=0 or column <=0 in Excel");
    }
    if(rowto != 0 && colto != 0)
    {
        if(rowto <= 0 || colto <= 0)
        {
            throw warning("We don`t have row <=0 or column <=0 in Excel");
        }
        if(colto <= 26)
        {
            strrange = num2char(colto+64) + int2str(rowto);
        }
        else
        {
            strrange = num2char((colto-1)/26+64)+num2char(((colto-1)mod 26)+65) + int2str(rowto);
        }
    }
    if(colfrom <= 26)
    {
        srange1 = num2char(colfrom+64) + int2str(rowfrom);
    }
    else
    {
        srange1=num2char((colfrom-1)/26+64)+num2char(((colfrom-1)mod 26)+65) + int2str(rowfrom);
    }
    if(rowto != 0 && colto != 0)
    {
        return srange1 + ":" + strrange;
    }
    else return srange1;
}