[string] Substring in VBA

I have multiple strings in different cells like

CO20:  20 YR CONVENTIONAL
FH30:  30 YR FHLMC
FHA31   

I need to get the substring from 1 to till index of ':' or if that is not available till ending(in case of string 3). I need help writing this in VBA.

You can first find the position of the string in this case ":"

'position = InStr(StringToSearch, StringToFind)
position = InStr(StringToSearch, ":")

Then use Left(StringToCut, NumberOfCharacterToCut)

Result = Left(StringToSearch, position -1)

Test for ':' first, then take test string up to ':' or end, depending on if it was found

Dim strResult As String

' Position of :
intPos = InStr(1, strTest, ":")
If intPos > 0 Then
    ' : found, so take up to :
    strResult = Left(strTest, intPos - 1)
Else
    ' : not found, so take whole string
    strResult = strTest
End If