Just to make sure that I have interpreted your question correctly ...
In: InStr(1, txtCol, "maint", vbTextCompare) "maint" and "Maint" are
considered equal. So, if the value of your control, txtCol, is: 123Maint,
the expression above will return 4.
In: InStr(1, txtCol, "maint", vbBinaryCompare) "maint" and "Maint" are
not equal. if the value of your control, txtCol, is: 123Maint, the
expression above will return 0.
hth,