I have a table as follows:

QTY     MAIN     LEN_FT     LEN_IN     WEIGHT      TWEIGHT .......
1        M        45           0         8580        8580
8                  2           6           39.3       314.40
2                  4           5          128.4       256.8
2        M        30           6         3960        7920
4                  3           0           50         200
1        M        45           0         8580        8580

What I need is one entry for each main, 'M', material that contains the length of the main material but the weight of the main material and the non main material directly following. For example:

QTY     MAIN     LEN_FT     LEN_IN     TWEIGHT    ........
1        M         45          0        9151.20
2        M         30          6        8120
1        M         45          0        8580 

Can someone please provide me with some suggestions on how to best accomplish this?

Thanks in advance,
Russell