How to change cell width w/o effecting other rows

[tqdinh22]

Can anyone tell me how to change the width of a cell withough effecting the width of the cells/rows below it...For example if you wanted A1 to stretch through the top of the worksheet overlapping B,C,D.... but only in row 1

Thanks

[MDubbelboer]

merge cell a1 into b1,c2,etc