You could either use Number Edit Box and then << Get or with Text Edit Box use << Get Text and then convert that to number with Num()
Names Default To Here(1);
//Text Edit Box
User_Input = New Window("N Col",
<<modal(),
H List Box(Text Box("Enter Column No: "), Col_Num_teb = Text Edit Box("", <<set width(200)), ),
Button Box("OK", col_num = col_num_teb << get text),
);
show(Num(col_num));
//number edit box
User_Input = New Window("N Col",
<<modal(),
H List Box(Text Box("Enter Column No: "), neb = Number Edit Box(., <<set width(50)), ),
Button Box("OK", col_num = neb << get),
);
show(col_num);
-Jarmo