The UBOUND function returns the largest valid index (upper bound) of an array dimension.
Syntax
result% = UBOUND(arrayName[, dimension%])
Description

arrayName specifies the name of the array.
 dimension% specifies the dimension number, starting with 1 for the first dimension.
 If omitted, dimension% is assumed to be 1.
 If dimension% is less than 1 or is greater than the number of dimensions, a ERROR Codes error occurs.
 UBOUND, along with LBOUND, is used to determine the range of valid indexes of an array.
Example(s)
DIM myArray(5) AS INTEGER
DIM myOtherArray(1 to 2, 3 to 4) AS INTEGER
PRINT UBOUND(myArray)
PRINT UBOUND(myOtherArray, 2)
5
4